Image decoding method and apparatus therefor

ABSTRACT

An image decoding method performed by a decoding apparatus according to the present document is characterized by comprising the steps of: acquiring image information; and generating a reconstructed picture on the basis of the image information.

BACKGROUND OF DISCLOSURE Field of the Disclosure

This document relates to image coding technology, and more specifically,to a video decoding method and apparatus in which flag information aboutwhether TSRC is enabled/disabled is coded based on flag informationabout whether SDH is enabled when coding residual data of a currentblock in an image coding system.

Related Art

Recently, demand for high-resolution, high-quality images, such as HighDefinition (HD) images and Ultra High Definition (UHD) images, has beenincreasing in various fields. As the image data has high resolution andhigh quality, the amount of information or bits to be transmittedincreases relative to the legacy image data. Therefore, when image datais transmitted using a medium such as a conventional wired/wirelessbroadband line or image data is stored using an existing storage medium,the transmission cost and the storage cost thereof are increased.

Accordingly, there is a need for a highly efficient image compressiontechnique for effectively transmitting, storing, and reproducinginformation of high-resolution and high-quality images.

SUMMARY

The present disclosure provides a method and apparatus for improvingimage coding efficiency.

The present disclosure also provides a method and apparatus forimproving residual coding efficiency.

According to an embodiment of this document, an image decoding methodperformed by a decoding apparatus is provided. The method includesobtaining image information, and generating a reconstructed picturebased on the image information.

According to another embodiment of this document, a decoding apparatusfor performing image decoding is provided. The decoding apparatusincludes an entropy decoder configured to obtain image information, anda residual processor configured to generate a reconstructed picturebased on the image information.

According to still another embodiment of this document, a video encodingmethod which is performed by an encoding apparatus is provided. Themethod includes generating a reconstructed picture for a current slice,and encoding image information for the current slice.

According to still another embodiment of this document, a video encodingapparatus is provided. The encoding apparatus includes a residualprocessor configured to generate a reconstructed picture for a currentslice, and an entropy encoder configured to encode image information forthe current slice.

According to still another embodiment of this document, there isprovided a computer-readable digital storage medium that stores abitstream including image information which causes a decoding apparatusto perform an image decoding method. In the computer-readable digitalstorage medium, the image decoding method includes obtaining imageinformation, and generating a reconstructed picture based on the imageinformation.

According to this document, it is possible to improve efficiency ofresidual coding.

According to this document, the TSRC enabled flag can be signaleddepending on the sign data hiding enabled flag, and through this, thecoding efficiency can be improved by preventing sign data hiding frombeing used for the transform skip block for which TSRC is not enabled,and the overall residual coding efficiency can be improved by reducingthe bit amount to be coded.

According to this document, the TSRC enabled flag can be signaleddepending on the transform skip enabled flag and the sign data hidingenabled flag, and through this, the coding efficiency can be improved bypreventing sign data hiding from being used for the transform skip blockfor which TSRC is not enabled, and the overall residual codingefficiency can be improved by reducing the bit amount to be coded.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 briefly illustrates an example of a video/image coding device towhich embodiments of the present disclosure are applicable.

FIG. 2 is a schematic diagram illustrating a configuration of avideo/image encoding apparatus to which the embodiment(s) of the presentdisclosure may be applied.

FIG. 3 is a schematic diagram illustrating a configuration of avideo/image decoding apparatus to which the embodiment(s) of the presentdisclosure may be applied.

FIG. 4 illustrates an example of an intra prediction-based video/imageencoding method.

FIG. 5 illustrates an example of an intra prediction-based video/imagedecoding method.

FIG. 6 schematically shows an intra prediction procedure.

FIG. 7 illustrates an example of an inter prediction-based video/imageencoding method.

FIG. 8 illustrates an example of an inter prediction-based video/imagedecoding method.

FIG. 9 schematically shows an inter prediction procedure.

FIG. 10 exemplarily shows context-adaptive binary arithmetic coding(CABAC) for encoding a syntax element.

FIG. 11 is a diagram showing exemplary transform coefficients within a4×4 block.

FIG. 12 briefly illustrates an image encoding method performed by anencoding apparatus according to the present disclosure.

FIG. 13 briefly illustrates an encoding apparatus for performing animage encoding method according to the present disclosure.

FIG. 14 briefly illustrates an image decoding method performed by adecoding apparatus according to the present disclosure.

FIG. 15 briefly illustrates a decoding apparatus for performing an imagedecoding method according to the present disclosure.

FIG. 16 illustrates a structural diagram of a contents streaming systemto which the present disclosure is applied.

DESCRIPTION OF EMBODIMENTS

The present disclosure may be modified in various forms, and specificembodiments thereof will be described and illustrated in the drawings.However, the embodiments are not intended for limiting the disclosure.The terms used in the following description are used to merely describespecific embodiments but are not intended to limit the disclosure. Anexpression of a singular number includes an expression of the pluralnumber, so long as it is clearly read differently. The terms such as“include” and “have” are intended to indicate that features, numbers,steps, operations, elements, components, or combinations thereof used inthe following description exist and it should be thus understood thatthe possibility of existence or addition of one or more differentfeatures, numbers, steps, operations, elements, components, orcombinations thereof is not excluded.

Meanwhile, elements in the drawings described in the disclosure areindependently drawn for the purpose of convenience for explanation ofdifferent specific functions, and do not mean that the elements areembodied by independent hardware or independent software. For example,two or more elements of the elements may be combined to form a singleelement, or one element may be partitioned into plural elements. Theembodiments in which the elements are combined and/or partitioned belongto the disclosure without departing from the concept of the disclosure.

Hereinafter, embodiments of the present disclosure will be described indetail with reference to the accompanying drawings. In addition, likereference numerals are used to indicate like elements throughout thedrawings, and the same descriptions on the like elements will beomitted.

FIG. 1 briefly illustrates an example of a video/image coding device towhich embodiments of the present disclosure are applicable.

Referring to FIG. 1 , a video/image coding system may include a firstdevice (source device) and a second device (receiving device). Thesource device may deliver encoded video/image information or data in theform of a file or streaming to the receiving device via a digitalstorage medium or network.

The source device may include a video source, an encoding apparatus, anda transmitter. The receiving device may include a receiver, a decodingapparatus, and a renderer. The encoding apparatus may be called avideo/image encoding apparatus, and the decoding apparatus may be calleda video/image decoding apparatus. The transmitter may be included in theencoding apparatus. The receiver may be included in the decodingapparatus. The renderer may include a display, and the display may beconfigured as a separate device or an external component.

The video source may acquire video/image through a process of capturing,synthesizing, or generating the video/image. The video source mayinclude a video/image capture device and/or a video/image generatingdevice. The video/image capture device may include, for example, one ormore cameras, video/image archives including previously capturedvideo/images, and the like. The video/image generating device mayinclude, for example, computers, tablets and smartphones, and may(electronically) generate video/images. For example, a virtualvideo/image may be generated through a computer or the like. In thiscase, the video/image capturing process may be replaced by a process ofgenerating related data.

The encoding apparatus may encode input image/image. The encodingapparatus may perform a series of procedures such as prediction,transform, and quantization for compression and coding efficiency. Theencoded data (encoded video/image information) may be output in the formof a bit stream.

The transmitter may transmit the encoded image/image information or dataoutput in the form of a bit stream to the receiver of the receivingdevice through a digital storage medium or a network in the form of afile or streaming. The digital storage medium may include variousstorage mediums such as USB, SD, CD, DVD, Blu-ray, HDD, SSD, and thelike. The transmitter may include an element for generating a media filethrough a predetermined file format and may include an element fortransmission through a broadcast/communication network. The receiver mayreceive/extract the bit stream and transmit the received bit stream tothe decoding apparatus.

The decoding apparatus may decode the video/image by performing a seriesof procedures such as dequantization, inverse transform, and predictioncorresponding to the operation of the encoding apparatus.

The renderer may render the decoded video/image. The renderedvideo/image may be displayed through the display.

Present disclosure relates to video/image coding. For example, themethods/embodiments disclosed in the present disclosure may be appliedto a method disclosed in the versatile video coding (VVC), the EVC(essential video coding) standard, the AOMedia Video 1 (AV1) standard,the 2nd generation of audio video coding standard (AVS2), or the nextgeneration video/image coding standard (e.g., H.267 or H.268, etc.).

Present disclosure presents various embodiments of video/image coding,and the embodiments may be performed in combination with each otherunless otherwise mentioned.

In the present disclosure, video may refer to a series of images overtime. Picture generally refers to a unit representing one image in aspecific time zone, and a subpicture/slice/tile is a unit constitutingpart of a picture in coding. The subpicture/slice/tile may include oneor more coding tree units (CTUs). One picture may consist of one or moresubpictures/slices/tiles. One picture may consist of one or more tilegroups. One tile group may include one or more tiles. A brick mayrepresent a rectangular region of CTU rows within a tile in a picture. Atile may be partitioned into multiple bricks, each of which consistingof one or more CTU rows within the tile. A tile that is not partitionedinto multiple bricks may be also referred to as a brick. A brick scan isa specific sequential ordering of CTUs partitioning a picture in whichthe CTUs are ordered consecutively in CTU raster scan in a brick, brickswithin a tile are ordered consecutively in a raster scan of the bricksof the tile, and tiles in a picture are ordered consecutively in araster scan of the tiles of the picture. In addition, a subpicture mayrepresent a rectangular region of one or more slices within a picture.That is, a subpicture contains one or more slices that collectivelycover a rectangular region of a picture. A tile is a rectangular regionof CTUs within a particular tile column and a particular tile row in apicture. The tile column is a rectangular region of CTUs having a heightequal to the height of the picture and a width specified by syntaxelements in the picture parameter set. The tile row is a rectangularregion of CTUs having a height specified by syntax elements in thepicture parameter set and a width equal to the width of the picture. Atile scan is a specific sequential ordering of CTUs partitioning apicture in which the CTUs are ordered consecutively in CTU raster scanin a tile whereas tiles in a picture are ordered consecutively in araster scan of the tiles of the picture. A slice includes an integernumber of bricks of a picture that may be exclusively contained in asingle NAL unit. A slice may consist of either a number of completetiles or only a consecutive sequence of complete bricks of one tile.Tile groups and slices may be used interchangeably in the presentdisclosure. For example, in the present disclosure, a tile group/tilegroup header may be called a slice/slice header.

A pixel or a pel may mean a smallest unit constituting one picture (orimage). Also, ‘sample’ may be used as a term corresponding to a pixel. Asample may generally represent a pixel or a value of a pixel, and mayrepresent only a pixel/pixel value of a luma component or only apixel/pixel value of a chroma component.

A unit may represent a basic unit of image processing. The unit mayinclude at least one of a specific region of the picture and informationrelated to the region. One unit may include one luma block and twochroma (e.g., cb, cr) blocks. The unit may be used interchangeably withterms such as block or area in some cases. In a general case, an M×Nblock may include samples (or sample arrays) or a set (or array) oftransform coefficients of M columns and N rows.

In the present description, “A or B” may mean “only A”, “only B” or“both A and B”. In other words, in the present specification, “A or B”may be interpreted as “A and/or B”. For example, “A, B or C” hereinmeans “only A”, “only B”, “only C”, or “any and any combination of A, Band C”.

A slash (/) or a comma (comma) used in the present description may mean“and/or”. For example, “A/B” may mean “A and/or B”. Accordingly, “A/B”may mean “only A”, “only B”, or “both A and B”. For example, “A, B, C”may mean “A, B, or C”.

In the present description, “at least one of A and B” may mean “only A”,“only B”, or “both A and B”. In addition, in the present description,the expression “at least one of A or B” or “at least one of A and/or B”may be interpreted the same as “at least one of A and B”.

In addition, in the present description, “at least one of A, B and C”means “only A”, “only B”, “only C”, or “any combination of A, B and C”.Also, “at least one of A, B or C” or “at least one of A, B and/or C” maymean “at least one of A, B and C”.

In addition, parentheses used in the present description may mean “forexample”. Specifically, when “prediction (intra prediction)” isindicated, “intra prediction” may be proposed as an example of“prediction”. In other words, “prediction” in the present description isnot limited to “intra prediction”, and “intra prediction” may beproposed as an example of “prediction”. Also, even when “prediction(i.e., intra prediction)” is indicated, “intra prediction” may beproposed as an example of “prediction”.

In the present description, technical features that are individuallydescribed within one drawing may be implemented individually or may beimplemented at the same time.

The following drawings were created to explain a specific example of thepresent description. Since the names of specific devices described inthe drawings or the names of specific signals/messages/fields arepresented by way of example, the technical features of the presentdescription are not limited to the specific names used in the followingdrawings.

FIG. 2 is a schematic diagram illustrating a configuration of avideo/image encoding apparatus to which the embodiment(s) of the presentdisclosure may be applied. Hereinafter, the video encoding apparatus mayinclude an image encoding apparatus.

Referring to FIG. 2 , the encoding apparatus 200 includes an imagepartitioner 210, a predictor 220, a residual processor 230, and anentropy encoder 240, an adder 250, a filter 260, and a memory 270. Thepredictor 220 may include an inter predictor 221 and an intra predictor222. The residual processor 230 may include a transformer 232, aquantizer 233, a dequantizer 234, and an inverse transformer 235. Theresidual processor 230 may further include a subtractor 231. The adder250 may be called a reconstructor or a reconstructed block generator.The image partitioner 210, the predictor 220, the residual processor230, the entropy encoder 240, the adder 250, and the filter 260 may beconfigured by at least one hardware component (e.g., an encoder chipsetor processor) according to an embodiment. In addition, the memory 270may include a decoded picture buffer (DPB) or may be configured by adigital storage medium. The hardware component may further include thememory 270 as an internal/external component.

The image partitioner 210 may partition an input image (or a picture ora frame) input to the encoding apparatus 200 into one or moreprocessors. For example, the processor may be called a coding unit (CU).In this case, the coding unit may be recursively partitioned accordingto a quad-tree binary-tree ternary-tree (QTBTTT) structure from a codingtree unit (CTU) or a largest coding unit (LCU). For example, one codingunit may be partitioned into a plurality of coding units of a deeperdepth based on a quad tree structure, a binary tree structure, and/or aternary structure. In this case, for example, the quad tree structuremay be applied first and the binary tree structure and/or ternarystructure may be applied later. Alternatively, the binary tree structuremay be applied first. The coding procedure according to the presentdisclosure may be performed based on the final coding unit that is nolonger partitioned. In this case, the largest coding unit may be used asthe final coding unit based on coding efficiency according to imagecharacteristics, or if necessary, the coding unit may be recursivelypartitioned into coding units of deeper depth and a coding unit havingan optimal size may be used as the final coding unit. Here, the codingprocedure may include a procedure of prediction, transform, andreconstruction, which will be described later. As another example, theprocessor may further include a prediction unit (PU) or a transform unit(TU). In this case, the prediction unit and the transform unit may besplit or partitioned from the aforementioned final coding unit. Theprediction unit may be a unit of sample prediction, and the transformunit may be a unit for deriving a transform coefficient and/or a unitfor deriving a residual signal from the transform coefficient.

The unit may be used interchangeably with terms such as block or area insome cases. In a general case, an M×N block may represent a set ofsamples or transform coefficients composed of M columns and N rows. Asample may generally represent a pixel or a value of a pixel, mayrepresent only a pixel/pixel value of a luma component or represent onlya pixel/pixel value of a chroma component. A sample may be used as aterm corresponding to one picture (or image) for a pixel or a pel.

In the encoding apparatus 200, a prediction signal (predicted block,prediction sample array) output from the inter predictor 221 or theintra predictor 222 is subtracted from an input image signal (originalblock, original sample array) to generate a residual signal residualblock, residual sample array), and the generated residual signal istransmitted to the transformer 232. In this case, as shown, a unit forsubtracting a prediction signal (predicted block, prediction samplearray) from the input image signal (original block, original samplearray) in the encoder 200 may be called a subtractor 231. The predictormay perform prediction on a block to be processed (hereinafter, referredto as a current block) and generate a predicted block includingprediction samples for the current block. The predictor may determinewhether intra prediction or inter prediction is applied on a currentblock or CU basis. As described later in the description of eachprediction mode, the predictor may generate various information relatedto prediction, such as prediction mode information, and transmit thegenerated information to the entropy encoder 240. The information on theprediction may be encoded in the entropy encoder 240 and output in theform of a bit stream.

The intra predictor 222 may predict the current block by referring tothe samples in the current picture. The referred samples may be locatedin the neighborhood of the current block or may be located apartaccording to the prediction mode. In the intra prediction, predictionmodes may include a plurality of non-directional modes and a pluralityof directional modes. The non-directional mode may include, for example,a DC mode and a planar mode. The directional mode may include, forexample, 33 directional prediction modes or 65 directional predictionmodes according to the degree of detail of the prediction direction.However, this is merely an example, more or less directional predictionmodes may be used depending on a setting. The intra predictor 222 maydetermine the prediction mode applied to the current block by using aprediction mode applied to a neighboring block.

The inter predictor 221 may derive a predicted block for the currentblock based on a reference block (reference sample array) specified by amotion vector on a reference picture. Here, in order to reduce theamount of motion information transmitted in the inter prediction mode,the motion information may be predicted in units of blocks, sub-blocks,or samples based on correlation of motion information between theneighboring block and the current block. The motion information mayinclude a motion vector and a reference picture index. The motioninformation may further include inter prediction direction (L0prediction, L1 prediction, Bi prediction, etc.) information. In the caseof inter prediction, the neighboring block may include a spatialneighboring block present in the current picture and a temporalneighboring block present in the reference picture. The referencepicture including the reference block and the reference pictureincluding the temporal neighboring block may be the same or different.The temporal neighboring block may be called a collocated referenceblock, a co-located CU (colCU), and the like, and the reference pictureincluding the temporal neighboring block may be called a collocatedpicture (colPic). For example, the inter predictor 221 may configure amotion information candidate list based on neighboring blocks andgenerate information indicating which candidate is used to derive amotion vector and/or a reference picture index of the current block.Inter prediction may be performed based on various prediction modes. Forexample, in the case of a skip mode and a merge mode, the interpredictor 221 may use motion information of the neighboring block asmotion information of the current block. In the skip mode, unlike themerge mode, the residual signal may not be transmitted. In the case ofthe motion vector prediction (MVP) mode, the motion vector of theneighboring block may be used as a motion vector predictor and themotion vector of the current block may be indicated by signaling amotion vector difference.

The predictor 220 may generate a prediction signal based on variousprediction methods described below. For example, the predictor may notonly apply intra prediction or inter prediction to predict one block butalso simultaneously apply both intra prediction and inter prediction.This may be called combined inter and intra prediction (CIIP). Inaddition, the predictor may be based on an intra block copy (IBC)prediction mode or a palette mode for prediction of a block. The IBCprediction mode or palette mode may be used for content image/videocoding of a game or the like, for example, screen content coding (SCC).The IBC basically performs prediction in the current picture but may beperformed similarly to inter prediction in that a reference block isderived in the current picture. That is, the IBC may use at least one ofthe inter prediction techniques described in the present disclosure. Thepalette mode may be considered as an example of intra coding or intraprediction. When the palette mode is applied, a sample value within apicture may be signaled based on information on the palette table andthe palette index.

The prediction signal generated by the predictor (including the interpredictor 221 and/or the intra predictor 222) may be used to generate areconstructed signal or to generate a residual signal. The transformer232 may generate transform coefficients by applying a transformtechnique to the residual signal. For example, the transform techniquemay include at least one of a discrete cosine transform (DCT), adiscrete sine transform (DST), a Karhunen-loéve transform (KLT), agraph-based transform (GBT), or a conditionally non-linear transform(CNT). Here, the GBT means transform obtained from a graph whenrelationship information between pixels is represented by the graph. TheCNT refers to transform generated based on a prediction signal generatedusing all previously reconstructed pixels. In addition, the transformprocess may be applied to square pixel blocks having the same size ormay be applied to blocks having a variable size rather than square.

The quantizer 233 may quantize the transform coefficients and transmitthem to the entropy encoder 240 and the entropy encoder 240 may encodethe quantized signal (information on the quantized transformcoefficients) and output a bit stream. The information on the quantizedtransform coefficients may be referred to as residual information. Thequantizer 233 may rearrange block type quantized transform coefficientsinto a one-dimensional vector form based on a coefficient scanning orderand generate information on the quantized transform coefficients basedon the quantized transform coefficients in the one-dimensional vectorform. Information on transform coefficients may be generated. Theentropy encoder 240 may perform various encoding methods such as, forexample, exponential Golomb, context-adaptive variable length coding(CAVLC), context-adaptive binary arithmetic coding (CABAC), and thelike. The entropy encoder 240 may encode information necessary forvideo/image reconstruction other than quantized transform coefficients(e.g., values of syntax elements, etc.) together or separately. Encodedinformation (e.g., encoded video/image information) may be transmittedor stored in units of NALs (network abstraction layer) in the form of abit stream. The video/image information may further include informationon various parameter sets such as an adaptation parameter set (APS), apicture parameter set (PPS), a sequence parameter set (SPS), or a videoparameter set (VPS). In addition, the video/image information mayfurther include general constraint information. In the presentdisclosure, information and/or syntax elements transmitted/signaled fromthe encoding apparatus to the decoding apparatus may be included invideo/picture information. The video/image information may be encodedthrough the above-described encoding procedure and included in the bitstream. The bit stream may be transmitted over a network or may bestored in a digital storage medium. The network may include abroadcasting network and/or a communication network, and the digitalstorage medium may include various storage media such as USB, SD, CD,DVD, Blu-ray, HDD, SSD, and the like. A transmitter (not shown)transmitting a signal output from the entropy encoder 240 and/or astorage unit (not shown) storing the signal may be included asinternal/external element of the encoding apparatus 200, andalternatively, the transmitter may be included in the entropy encoder240.

The quantized transform coefficients output from the quantizer 233 maybe used to generate a prediction signal. For example, the residualsignal (residual block or residual samples) may be reconstructed byapplying dequantization and inverse transform to the quantized transformcoefficients through the dequantizer 234 and the inverse transformer235. The adder 250 adds the reconstructed residual signal to theprediction signal output from the inter predictor 221 or the intrapredictor 222 to generate a reconstructed signal (reconstructed picture,reconstructed block, reconstructed sample array). If there is noresidual for the block to be processed, such as a case where the skipmode is applied, the predicted block may be used as the reconstructedblock. The adder 250 may be called a reconstructor or a reconstructedblock generator. The generated reconstructed signal may be used forintra prediction of a next block to be processed in the current pictureand may be used for inter prediction of a next picture through filteringas described below.

Meanwhile, luma mapping with chroma scaling (LMCS) may be applied duringpicture encoding and/or reconstruction.

The filter 260 may improve subjective/objective image quality byapplying filtering to the reconstructed signal. For example, the filter260 may generate a modified reconstructed picture by applying variousfiltering methods to the reconstructed picture and store the modifiedreconstructed picture in the memory 270, specifically, a DPB of thememory 270. The various filtering methods may include, for example,deblocking filtering, a sample adaptive offset, an adaptive loop filter,a bilateral filter, and the like. The filter 260 may generate variousinformation related to the filtering and transmit the generatedinformation to the entropy encoder 240 as described later in thedescription of each filtering method. The information related to thefiltering may be encoded by the entropy encoder 240 and output in theform of a bit stream.

The modified reconstructed picture transmitted to the memory 270 may beused as the reference picture in the inter predictor 221. When the interprediction is applied through the encoding apparatus, predictionmismatch between the encoding apparatus 200 and the decoding apparatus300 may be avoided and encoding efficiency may be improved.

The DPB of the memory 270 DPB may store the modified reconstructedpicture for use as a reference picture in the inter predictor 221. Thememory 270 may store the motion information of the block from which themotion information in the current picture is derived (or encoded) and/orthe motion information of the blocks in the picture that have alreadybeen reconstructed. The stored motion information may be transmitted tothe inter predictor 221 and used as the motion information of thespatial neighboring block or the motion information of the temporalneighboring block. The memory 270 may store reconstructed samples ofreconstructed blocks in the current picture and may transfer thereconstructed samples to the intra predictor 222.

FIG. 3 is a schematic diagram illustrating a configuration of avideo/image decoding apparatus to which the embodiment(s) of the presentdisclosure may be applied.

Referring to FIG. 3 , the decoding apparatus 300 may include an entropydecoder 310, a residual processor 320, a predictor 330, an adder 340, afilter 350, and a memory 360. The predictor 330 may include an interpredictor 331 and an intra predictor 332. The residual processor 320 mayinclude a dequantizer 321 and an inverse transformer 322. The entropydecoder 310, the residual processor 320, the predictor 330, the adder340, and the filter 350 may be configured by a hardware component (e.g.,a decoder chipset or a processor) according to an embodiment. Inaddition, the memory 360 may include a decoded picture buffer (DPB) ormay be configured by a digital storage medium. The hardware componentmay further include the memory 360 as an internal/external component.

When a bit stream including video/image information is input, thedecoding apparatus 300 may reconstruct an image corresponding to aprocess in which the video/image information is processed in theencoding apparatus of FIG. 2 . For example, the decoding apparatus 300may derive units/blocks based on block partition related informationobtained from the bit stream. The decoding apparatus 300 may performdecoding using a processor applied in the encoding apparatus. Thus, theprocessor of decoding may be a coding unit, for example, and the codingunit may be partitioned according to a quad tree structure, binary treestructure and/or ternary tree structure from the coding tree unit or thelargest coding unit. One or more transform units may be derived from thecoding unit. The reconstructed image signal decoded and output throughthe decoding apparatus 300 may be reproduced through a reproducingapparatus.

The decoding apparatus 300 may receive a signal output from the encodingapparatus of FIG. 2 in the form of a bit stream, and the received signalmay be decoded through the entropy decoder 310. For example, the entropydecoder 310 may parse the bit stream to derive information (e.g.,video/image information) necessary for image reconstruction (or picturereconstruction). The video/image information may further includeinformation on various parameter sets such as an adaptation parameterset (APS), a picture parameter set (PPS), a sequence parameter set(SPS), or a video parameter set (VPS). In addition, the video/imageinformation may further include general constraint information. Thedecoding apparatus may further decode picture based on the informationon the parameter set and/or the general constraint information.Signaled/received information and/or syntax elements described later inthe present disclosure may be decoded may decode the decoding procedureand obtained from the bit stream. For example, the entropy decoder 310decodes the information in the bit stream based on a coding method suchas exponential Golomb coding, CAVLC, or CABAC, and output syntaxelements required for image reconstruction and quantized values oftransform coefficients for residual. More specifically, the CABACentropy decoding method may receive a bin corresponding to each syntaxelement in the bit stream, determine a context model using a decodingtarget syntax element information, decoding information of a decodingtarget block or information of a symbol/bin decoded in a previous stage,and perform an arithmetic decoding on the bin by predicting aprobability of occurrence of a bin according to the determined contextmodel, and generate a symbol corresponding to the value of each syntaxelement. In this case, the CABAC entropy decoding method may update thecontext model by using the information of the decoded symbol/bin for acontext model of a next symbol/bin after determining the context model.The information related to the prediction among the information decodedby the entropy decoder 310 may be provided to the predictor (the interpredictor 332 and the intra predictor 331), and the residual value onwhich the entropy decoding was performed in the entropy decoder 310,that is, the quantized transform coefficients and related parameterinformation, may be input to the residual processor 320. The residualprocessor 320 may derive the residual signal (the residual block, theresidual samples, the residual sample array). In addition, informationon filtering among information decoded by the entropy decoder 310 may beprovided to the filter 350. Meanwhile, a receiver (not shown) forreceiving a signal output from the encoding apparatus may be furtherconfigured as an internal/external element of the decoding apparatus300, or the receiver may be a component of the entropy decoder 310.Meanwhile, the decoding apparatus according to the present disclosuremay be referred to as a video/image/picture decoding apparatus, and thedecoding apparatus may be classified into an information decoder(video/image/picture information decoder) and a sample decoder(video/image/picture sample decoder). The information decoder mayinclude the entropy decoder 310, and the sample decoder may include atleast one of the dequantizer 321, the inverse transformer 322, the adder340, the filter 350, the memory 360, the inter predictor 332, and theintra predictor 331.

The dequantizer 321 may dequantize the quantized transform coefficientsand output the transform coefficients. The dequantizer 321 may rearrangethe quantized transform coefficients in the form of a two-dimensionalblock form. In this case, the rearrangement may be performed based onthe coefficient scanning order performed in the encoding apparatus. Thedequantizer 321 may perform dequantization on the quantized transformcoefficients by using a quantization parameter (e.g., quantization stepsize information) and obtain transform coefficients.

The inverse transformer 322 inversely transforms the transformcoefficients to obtain a residual signal (residual block, residualsample array).

The predictor may perform prediction on the current block and generate apredicted block including prediction samples for the current block. Thepredictor may determine whether intra prediction or inter prediction isapplied to the current block based on the information on the predictionoutput from the entropy decoder 310 and may determine a specificintra/inter prediction mode.

The predictor 320 may generate a prediction signal based on variousprediction methods described below. For example, the predictor may notonly apply intra prediction or inter prediction to predict one block butalso simultaneously apply intra prediction and inter prediction. Thismay be called combined inter and intra prediction (CIIP). In addition,the predictor may be based on an intra block copy (IBC) prediction modeor a palette mode for prediction of a block. The IBC prediction mode orpalette mode may be used for content image/video coding of a game or thelike, for example, screen content coding (SCC). The IBC basicallyperforms prediction in the current picture but may be performedsimilarly to inter prediction in that a reference block is derived inthe current picture. That is, the IBC may use at least one of the interprediction techniques described in the present disclosure. The palettemode may be considered as an example of intra coding or intraprediction. When the palette mode is applied, a sample value within apicture may be signaled based on information on the palette table andthe palette index.

The intra predictor 331 may predict the current block by referring tothe samples in the current picture. The referred samples may be locatedin the neighborhood of the current block or may be located apartaccording to the prediction mode. In the intra prediction, predictionmodes may include a plurality of non-directional modes and a pluralityof directional modes. The intra predictor 331 may determine theprediction mode applied to the current block by using a prediction modeapplied to a neighboring block.

The inter predictor 332 may derive a predicted block for the currentblock based on a reference block (reference sample array) specified by amotion vector on a reference picture. In this case, in order to reducethe amount of motion information transmitted in the inter predictionmode, motion information may be predicted in units of blocks,sub-blocks, or samples based on correlation of motion informationbetween the neighboring block and the current block. The motioninformation may include a motion vector and a reference picture index.The motion information may further include inter prediction direction(L0 prediction, L1 prediction, Bi prediction, etc.) information. In thecase of inter prediction, the neighboring block may include a spatialneighboring block present in the current picture and a temporalneighboring block present in the reference picture. For example, theinter predictor 332 may configure a motion information candidate listbased on neighboring blocks and derive a motion vector of the currentblock and/or a reference picture index based on the received candidateselection information. Inter prediction may be performed based onvarious prediction modes, and the information on the prediction mayinclude information indicating a mode of inter prediction for thecurrent block.

The adder 340 may generate a reconstructed signal (reconstructedpicture, reconstructed block, reconstructed sample array) by adding theobtained residual signal to the prediction signal (predicted block,predicted sample array) output from the predictor (including the interpredictor 332 and/or the intra predictor 331). If there is no residualfor the block to be processed, such as when the skip mode is applied,the predicted block may be used as the reconstructed block.

The adder 340 may be called reconstructor or a reconstructed blockgenerator. The generated reconstructed signal may be used for intraprediction of a next block to be processed in the current picture, maybe output through filtering as described below, or may be used for interprediction of a next picture.

Meanwhile, luma mapping with chroma scaling (LMCS) may be applied in thepicture decoding process.

The filter 350 may improve subjective/objective image quality byapplying filtering to the reconstructed signal. For example, the filter350 may generate a modified reconstructed picture by applying variousfiltering methods to the reconstructed picture and store the modifiedreconstructed picture in the memory 360, specifically, a DPB of thememory 360. The various filtering methods may include, for example,deblocking filtering, a sample adaptive offset, an adaptive loop filter,a bilateral filter, and the like.

The (modified) reconstructed picture stored in the DPB of the memory 360may be used as a reference picture in the inter predictor 332. Thememory 360 may store the motion information of the block from which themotion information in the current picture is derived (or decoded) and/orthe motion information of the blocks in the picture that have alreadybeen reconstructed. The stored motion information may be transmitted tothe inter predictor 260 so as to be utilized as the motion informationof the spatial neighboring block or the motion information of thetemporal neighboring block. The memory 360 may store reconstructedsamples of reconstructed blocks in the current picture and transfer thereconstructed samples to the intra predictor 331.

In the present disclosure, the embodiments described in the filter 260,the inter predictor 221, and the intra predictor 222 of the encodingapparatus 200 may be the same as or respectively applied to correspondto the filter 350, the inter predictor 332, and the intra predictor 331of the decoding apparatus 300. The same may also apply to the unit 332and the intra predictor 331.

In the present disclosure, at least one of quantization/inversequantization and/or transform/inverse transform may be omitted. When thequantization/inverse quantization is omitted, the quantized transformcoefficients may be called transform coefficients. When thetransform/inverse transform is omitted, the transform coefficients maybe called coefficients or residual coefficients, or may still be calledtransform coefficients for uniformity of expression.

In the present disclosure, a quantized transform coefficient and atransform coefficient may be referred to as a transform coefficient anda scaled transform coefficient, respectively. In this case, the residualinformation may include information on transform coefficient(s), and theinformation on the transform coefficient(s) may be signaled throughresidual coding syntax. Transform coefficients may be derived based onthe residual information (or the information on the transformcoefficient(s)), and scaled transform coefficients may be derived byinverse transforming (scaling) on the transform coefficients. Residualsamples may be derived based on the inverse transforming (transforming)on the scaled transform coefficients. This may be applied/expressed inother parts of the present disclosure as well.

Meanwhile, as described above, in performing video coding, prediction isperformed to improve compression efficiency. Through this, a predictedblock including prediction samples for a current block as a block to becoded (i.e., a coding target block) may be generated. Here, thepredicted block includes prediction samples in a spatial domain (orpixel domain). The predicted block is derived in the same manner in anencoding apparatus and a decoding apparatus, and the encoding apparatusmay signal information (residual information) on residual between theoriginal block and the predicted block, rather than an original samplevalue of an original block, to the decoding apparatus, therebyincreasing image coding efficiency. The decoding apparatus may derive aresidual block including residual samples based on the residualinformation, add the residual block and the predicted block to generatereconstructed blocks including reconstructed samples, and generate areconstructed picture including the reconstructed blocks.

The residual information may be generated through a transform andquantization procedure. For example, the encoding apparatus may derive aresidual block between the original block and the predicted block,perform a transform procedure on residual samples (residual samplearray) included in the residual block to derive transform coefficients,perform a quantization procedure on the transform coefficients to derivequantized transform coefficients, and signal related residualinformation to the decoding apparatus (through a bit stream). Here, theresidual information may include value information of the quantizedtransform coefficients, location information, a transform technique, atransform kernel, a quantization parameter, and the like. The decodingapparatus may perform dequantization/inverse transform procedure basedon the residual information and derive residual samples (or residualblocks). The decoding apparatus may generate a reconstructed picturebased on the predicted block and the residual block. Also, for referencefor inter prediction of a picture afterward, the encoding apparatus mayalso dequantize/inverse-transform the quantized transform coefficientsto derive a residual block and generate a reconstructed picture basedthereon.

Intra prediction may refer to prediction that generates predictionsamples for a current block based on reference samples in a picture towhich the current block belongs (hereinafter, referred to as a currentpicture). When the intra prediction is applied to the current block,neighboring reference samples to be used for the intra prediction of thecurrent block may be derived. The neighboring reference samples of thecurrent block may include a sample adjacent to the left boundary of thecurrent block of size nW×nH and a total of 2×nH samples adjacent to thebottom-left of the current block, a sample adjacent to the top boundaryof the current block and a total of 2×nW samples adjacent to thetop-right and a sample adjacent to the top-left of the current block.Alternatively, the neighboring reference samples of the current blockmay include a plurality of columns of top neighboring samples and aplurality of rows of left neighboring samples. In addition, theneighboring reference samples of the current block may include a totalof nH samples adjacent to the right boundary of the current block ofsize nW×nH, a total of nW samples adjacent to the bottom boundary of thecurrent block and a sample adjacent to the bottom-right of the currentblock.

However, some of the neighboring reference samples of the current blockhave not yet been decoded or may not be available. In this case, thedecoder may construct neighboring reference samples to be used forprediction by substituting unavailable samples with available samples.Alternatively, neighboring reference samples to be used for predictionmay be configured through interpolation of available samples.

When the neighboring reference samples are derived, (i) a predictionsample may be derived based on the average or interpolation ofneighboring reference samples of the current block, or (ii) theprediction sample may be derived based on a reference sample existing ina specific (prediction) direction with respect to a prediction sampleamong the neighboring reference samples of the current block. The caseof (i) may be called a non-directional mode or a non-angular mode, andthe case of (ii) may be called a directional mode or an angular mode.

In addition, the prediction sample may be generated throughinterpolation of a first neighboring sample located in the predictiondirection of the intra prediction mode of the current block based on theprediction sample of the current block and a second neighboring samplelocated in a direction opposite to the prediction direction among theneighboring reference samples. The above-described case may be referredto as linear interpolation intra prediction (LIP). In addition, chromaprediction samples may be generated based on the luma samples using alinear model (LM). This case may be called an LM mode or a chromacomponent LM (CCLM) mode.

In addition, a temporary prediction sample of the current block isderived based on the filtered neighboring reference samples, and aprediction sample of the current block may also be derived by weightedsumming the temporary prediction sample and at least one referencesample derived according to the intra prediction mode among the existingneighboring reference samples, that is, unfiltered neighboring referencesamples. The above-described case may be referred to as positiondependent intra prediction (PDPC).

In addition, a reference sample line with the highest predictionaccuracy among neighboring multiple reference sample lines of thecurrent block is selected, and a prediction sample is derived using areference sample located in the prediction direction in the selectedline. In this case, intra prediction encoding may be performed byindicating (signaling) the used reference sample line to the decodingapparatus. The above-described case may be referred to asmulti-reference line intra prediction or MRL-based intra prediction.

In addition, the current block is divided into vertical or horizontalsub-partitions and intra prediction is performed based on the same intraprediction mode, but neighboring reference samples may be derived andused in units of the sub-partitions. That is, in this case, the intraprediction mode for the current block is equally applied to thesub-partitions, but the intra prediction performance may be improved insome cases by deriving and using the neighboring reference samples inunits of the sub-partitions. This prediction method may be calledintra-prediction based on intra sub-partitions (ISP).

The above-described intra prediction methods may be called intraprediction types to be distinguished from the intra prediction mode. Theintra prediction types may be referred to by various terms such as intraprediction technique or additional intra prediction modes. For example,the intra prediction types (or additional intra prediction modes, etc.)may include at least one of the aforementioned LIP, PDPC, MRL, and ISP.A general intra prediction method excluding a specific intra predictiontype such as LIP, PDPC, MRL, and ISP may be referred to as a normalintra prediction type. The normal intra prediction type may be generallyapplied when the above specific intra prediction type is not applied,and prediction may be performed based on the above-described intraprediction mode. Meanwhile, if necessary, post-processing filtering maybe performed on the derived prediction sample.

Specifically, the intra prediction process may include an intraprediction mode/type determination step, neighboring reference samplesderivation step, and an intra prediction mode/type based predictionsample derivation step. In addition, if necessary, a post-filtering stepmay be performed on the derived prediction sample.

FIG. 4 illustrates an example of an intra prediction-based video/imageencoding method.

Referring to FIG. 4 , the encoding device performs intra prediction onthe current block S400. The encoding device derives an intra predictionmode/type for the current block, derives neighboring reference samplesof the current block, generates prediction samples in the current blockbased on the intra prediction mode/type and the neighboring referencesamples. Here, the intra prediction mode/type determination, neighboringreference samples derivation, and prediction samples generationprocedures may be performed simultaneously, or one procedure may beperformed before another procedure. The encoding device may determine amode/type applied to the current block from among a plurality of intraprediction modes/types. The encoding device may compare RD costs for theintra prediction mode/types and determine an optimal intra predictionmode/type for the current block.

Meanwhile, the encoding device may perform a prediction sample filteringprocedure. The prediction sample filtering may be referred to as postfiltering. Some or all of the prediction samples may be filtered by theprediction sample filtering procedure. In some cases, the predictionsample filtering procedure may be omitted.

The encoding device generates residual samples for the current blockbased on the (filtered) prediction samples S410. The encoding device maycompare the prediction samples in the original samples of the currentblock based on the phase and derive the residual samples.

The encoding device may encode image information including informationon the intra prediction (prediction information) and residualinformation on the residual samples S420. The prediction information mayinclude the intra prediction mode information and the intra predictiontype information. The encoding device may output encoded imageinformation in the form of a bitstream. The output bitstream may betransmitted to the decoding device through a storage medium or anetwork.

The residual information may include residual coding syntax, which willbe described later. The encoding device may transform/quantize theresidual samples to derive quantized transform coefficients. Theresidual information may include information on the quantized transformcoefficients.

Meanwhile, as described above, the encoding device may generate areconstructed picture (including reconstructed samples and reconstructedblocks). To this end, the encoding device may derive (modified) residualsamples by performing inverse quantization/inverse transformation on thequantized transform coefficients again. The reason for performing theinverse quantization/inverse transformation again aftertransforming/quantizing the residual samples in this way is to derivethe same residual samples as the residual samples derived in thedecoding device as described above. The encoding device may generate areconstructed block including reconstructed samples for the currentblock based on the prediction samples and the (modified) residualsamples. A reconstructed picture for the current picture may begenerated based on the reconstructed block. As described above, anin-loop filtering procedure may be further applied to the reconstructedpicture.

FIG. 5 illustrates an example of an intra prediction-based video/imagedecoding method.

The decoding device may perform an operation corresponding to theoperation performed by the encoding apparatus.

Prediction information and residual information may be obtained from abitstream. Residual samples for the current block may be derived basedon the residual information. Specifically, transform coefficients may bederived by performing inverse quantization based on the quantizedtransform coefficients derived based on the residual information,residual samples for the current block may be derived by performinginverse transform on the transform coefficients.

Specifically, the decoding device may derive the intra predictionmode/type for the current block based on the received predictioninformation (intra prediction mode/type information) S500. The decodingdevice may derive neighboring reference samples of the current blockS510. The decoding device generates prediction samples in the currentblock based on the intra prediction mode/type and the neighboringreference samples S520. In this case, the decoding device may perform aprediction sample filtering procedure. The Predictive sample filteringmay be referred to as post filtering. Some or all of the predictionsamples may be filtered by the prediction sample filtering procedure. Insome cases, the prediction sample filtering procedure may be omitted.

The decoding device generates residual samples for the current blockbased on the received residual information S530. The decoding device maygenerate reconstructed samples for the current block based on theprediction samples and the residual samples, and may derive areconstructed block including the reconstructed samples S540. Areconstructed picture for the current picture may be generated based onthe reconstructed block. As described above, an in-loop filteringprocedure may be further applied to the reconstructed picture.

The intra prediction mode information may include, for example, flaginformation (ex. intra_luma_mpm_flag) indicating whether MPM (mostprobable mode) is applied to the current block or whether a remainingmode is applied, and, when the MPM is applied to the current block, theprediction mode information may further include index information (eg,intra_luma_mpm_idx) indicating one of the intra prediction modecandidates (MPM candidates). The intra prediction mode candidates (MPMcandidates) may be constructed of an MPM candidate list or an MPM list.In addition, when the MPM is not applied to the current block, the intraprediction mode information includes remaining mode information (ex.intra_luma_mpm_remainder) indicating one of the remaining intraprediction modes except for the intra prediction mode candidates (MPMcandidates). The decoding device may determine the intra prediction modeof the current block based on the intra prediction mode information.

Also, the intra prediction type information may be implemented invarious forms. For example, the intra prediction type information mayinclude intra prediction type index information indicating one of theintra prediction types. As another example, the intra prediction typeinformation may include at least one of reference sample lineinformation (ex. intra_luma_ref_idx) representing whether the MRL isapplied to the current block and, if applied, which reference sampleline is used, ISP flag information representing whether the ISP isapplied to the current block (ex. intra_subpartitions_mode_flag), ISPtype information indicating a split type of subpartitions when the ISPis applied (ex. intra_subpartitions_split_flag), flag informationrepresenting whether the PDPC is applied or flag informationrepresenting whether the LIP is applied. Also, the intra prediction typeinformation may include a MIP flag representing whether matrix-basedintra prediction (MIP) is applied to the current block.

The intra prediction mode information and/or the intra prediction typeinformation may be encoded/decoded through a coding method described inthe present disclosure. For example, the intra prediction modeinformation and/or the intra prediction type information may beencoded/decoded through entropy coding (e.g., CABAC, CAVLC).

FIG. 6 schematically shows an intra prediction procedure.

Referring to FIG. 6 , as described above, the intra prediction proceduremay include a step of determinating an intra prediction mode/type, astep of deriving neighboring reference samples, and a step of performingintra prediction (generating a prediction sample). The intra predictionprocedure may be performed by the encoding device and the decodingdevice as described above. In the present disclosure, a coding devicemay include the encoding device and/or the decoding device.

Referring to FIG. 6 , the coding device determines an intra predictionmode/type S600.

The encoding device may determine an intra prediction mode/type appliedto the current block from among the various intra prediction modes/typesdescribed above, and may generate prediction related information. Theprediction related information may include intra prediction modeinformation representing an intra prediction mode applied to the currentblock and/or intra prediction type information representing an intraprediction type applied to the current block. The decoding device maydetermine an intra prediction mode/type applied to the current blockbased on the prediction related information.

The intra prediction mode information may include, for example, flaginformation (ex. intra_luma_mpm_flag) representing whether a mostprobable mode (MPM) is applied to the current block or a remaining modeis applied, and the When the MPM is applied to the current block, theprediction mode information may further include index information (eg,intra_luma_mpm_idx) indicating one of the intra prediction modecandidates (MPM candidates). The intra prediction mode candidates (MPMcandidates) may be constructed of an MPM candidate list or an MPM list.In addition, when the MPM is not applied to the current block, the intraprediction mode information may further include remaining modeinformation (ex. intra_luma_mpm_remainder) indicating one of theremaining intra prediction modes except for the intra prediction modecandidates (MPM candidates). The decoding device may determine the intraprediction mode of the current block based on the intra prediction modeinformation.

In addition, the intra prediction type information may be implemented invarious forms. For example, the intra prediction type information mayinclude intra prediction type index information indicating one of theintra prediction types. As another example, the intra prediction typeinformation may include at least one of reference sample lineinformation (ex. intra_luma_ref_idx) representing whether the MRL isapplied to the current block and, if applied, which reference sampleline is used, ISP flag information representing whether the ISP isapplied to the current block (ex. intra_subpartitions_mode_flag), ISPtype information indicating a split type of subpartitions when the ISPis applied (ex. intra_subpartitions_split_flag), flag informationrepresenting whether the PDPC is applied or flag informationrepresenting whether the LIP is applied. Also, the intra prediction typeinformation may include a MIP flag representing whether matrix-basedintra prediction (MIP) is applied to the current block.

For example, when intra prediction is applied, an intra prediction modeapplied to the current block may be determined using an intra predictionmode of a neighboring block. For example, the coding device may selectone of most probable mode (MPM) candidates in the MPM list derived basedon additional candidate modes and/or an intra prediction mode of theneighboring block (eg, the left and/or top neighboring block) of thecurrent block, or select one of the remaining intra prediction modes notincluded in the MPM candidates (and planar mode) based on the MPMremainder information (remaining intra prediction mode information). TheMPM list may be configured to include or not include the planner mode asa candidate. For example, when the MPM list includes a planner mode as acandidate, the MPM list may have 6 candidates, and when the MPM listdoes not include a planner mode as a candidate, the MPM list may have 5candidates. When the MPM list does not include the planar mode as acandidate, a not planar flag (ex. intra_luma_not_planar flag)representing whether the intra prediction mode of the current block isnot the planar mode may be signaled. For example, the MPM flag may besignaled first, and the MPM index and not planner flag may be signaledwhen the value of the MPM flag is 1. Also, the MPM index may be signaledwhen the value of the not planner flag is 1. Here, the fact that the MPMlist is configured not to include the planner mode as a candidate isthat the planner mode is always considered as MPM rather than that theplanner mode is not MPM, thus, the flag (not planar flag) is signaledfirst to check whether it is the planar mode.

For example, whether the intra prediction mode applied to the currentblock is among the MPM candidates (and the planar mode) or the remainingmodes may be indicated based on the MPM flag (eg, intra_luma_mpm_flag).The MPM flag with a value of 1 may indicate that the intra predictionmode for the current block is within MPM candidates (and planar mode),and The MPM flag with a value of 0 may indicate that the intraprediction mode for the current block is not within MPM candidates (andplanar mode). The not planar flag (ex. intra_luma_not_planar flag) witha value of 0 may indicate that the intra prediction mode for the currentblock is a planar mode, and the not planar flag with a value of 1 mayindicate that the intra prediction mode for the current block is not theplanar mode. The MPM index may be signaled in the form of an mpm_idx orintra_luma_mpm_idx syntax element, and the remaining intra predictionmode information may be signaled in the form of arem_intra_luma_pred_mode or intra_luma_mpm_remainder syntax element. Forexample, the remaining intra prediction mode information may indicateone of the remaining intra prediction modes not included in the MPMcandidates (and planar mode) among all intra prediction modes byindexing in the order of prediction mode number. The intra predictionmode may be an intra prediction mode for a luma component (sample).Hereinafter, the intra prediction mode information may include at leastone of the MPM flag (ex. intra_luma_mpm_flag), the not planar flag (ex.intra_luma_not_planar flag), the MPM index (ex. mpm_idx orintra_luma_mpm_idx), or the remaining intra prediction mode information(rem_intra_luma_luma_mpm_mode or intra_luma_mpminder). In the presentdisclosure, the MPM list may be referred to by various terms such as anMPM candidate list and candModeList.

When the MIP is applied to the current block, a separate mpm flag (ex.intra_mip_mpm_flag) for the MIP, an mpm index (ex. intra_mip_mpm_idx),and remaining intra prediction mode information (ex.intra_mip_mpm_remainder) may be signaled, and the not planar flag maynot be signaled.

In other words, in general, when a block partition for an image isperformed, the current block to be coded and a neighboring block havesimilar image characteristics. Therefore, there is a high probabilitythat the current block and the neighboring block have the same orsimilar intra prediction mode. Accordingly, the encoder may use theintra prediction mode of the neighboring block to encode the intraprediction mode of the current block.

The coding device may construct a most probable modes (MPM) list for thecurrent block. The MPM list may be referred to as the MPM candidatelist. Here, the MPM may refer to modes used to improve coding efficiencyin consideration of the similarity between the current block and theneighboring blocks during intra prediction mode coding. As describedabove, the MPM list may be constructed to include the planar mode, ormay be constructed to exclude the planar mode. For example, when the MPMlist includes the planar mode, the number of candidates in the MPM listmay be 6. And, when the MPM list does not include the planar mode, thenumber of candidates in the MPM list may be 5.

The encoding device may perform prediction based on various intraprediction modes, and may determine an optimal intra prediction modebased on rate-distortion optimization (RDO) based thereon. In this case,the encoding device may determine the optimal intra prediction mode byusing only the MPM candidates and planar mode configured in the MPMlist, or by further using the remaining intra prediction modes as wellas the MPM candidates and planar mode configured in the MPM list.Specifically, for example, if the intra prediction type of the currentblock is a specific type (ex. LIP, MRL, or ISP) other than the normalintra prediction type, the encoding device may determine the optimalintra prediction mode by considering only the MPM candidates and theplanar mode as intra prediction mode candidates for the current block.That is, in this case, the intra prediction mode for the current blockmay be determined only from among the MPM candidates and the planarmode, and in this case, encoding/signaling of the mpm flag may not beperformed. In this case, the decoding device may infer that the mpm flagis 1 without separately signaling the mpm flag.

Meanwhile, in general, when the intra prediction mode of the currentblock is not the planar mode and is one of the MPM candidates in the MPMlist, the encoding device generates an mpm index (mpm idx) indicatingone of the MPM candidates. when the intra prediction mode of the currentblock is not included in the MPM list, the encoding device generates MPMreminder information (remaining intra prediction mode information)indicating the same mode as the intra prediction mode of the currentblock among the remaining intra prediction modes not included in the MPMlist (and planar mode). The MPM reminder information may include, forexample, an intra_luma_mpm_remainder syntax element.

The decoding device obtains intra prediction mode information from thebitstream. As described above, the intra prediction mode information mayinclude at least one of an MPM flag, a not planner flag, an MPM index,and MPM remaster information (remaining intra prediction modeinformation). The decoding device may construct the MPM list. The MPMlist is constructed the same as the MPM list constructed in the encodingdevice. That is, the MPM list may include intra prediction modes ofneighboring blocks, or may further include specific intra predictionmodes according to a predetermined method.

The decoding device may determine the intra prediction mode of thecurrent block based on the MPM list and the intra prediction modeinformation. For example, when the value of the MPM flag is 1, thedecoding device may derive the planar mode as the intra prediction modeof the current block (based on not planar flag) or derive the candidateindicated by the MPM index from among the MPM candidates in the MPM listas the intra prediction mode of the current block. Here, the MPMcandidates may represent only candidates included in the MPM list, ormay include not only candidates included in the MPM list but also theplanar mode applicable when the value of the MPM flag is 1.

As another example, when the value of the MPM flag is 0, the decodingdevice may derive an intra prediction mode indicated by the remainingintra prediction mode information (which may be referred to as mpmremainder information) among the remaining intra prediction modes notincluded in the MPM list and the planner mode as the intra predictionmode of the current block. Meanwhile, as another example, when the intraprediction type of the current block is a specific type (ex. LIP, MRL orISP, etc.), the decoding device may derive a candidate indicated by theMPM flag in the planar mode or the MPM list as the intra prediction modeof the current block without parsing/decoding/checking the MPM flag.

The coding device derives neighboring reference samples of the currentblock S610. When intra prediction is applied to the current block, theneighboring reference samples to be used for the intra prediction of thecurrent block may be derived. The neighboring reference samples of thecurrent block may include a sample adjacent to the left boundary of thecurrent block of size nW×nH and a total of 2×nH samples adjacent to thebottom-left of the current block, a sample adjacent to the top boundaryof the current block and a total of 2×nW samples adjacent to thetop-right and a sample adjacent to the top-left of the current block.Alternatively, the neighboring reference samples of the current blockmay include a plurality of columns of top neighboring samples and aplurality of rows of left neighboring samples. In addition, theneighboring reference samples of the current block may include a totalof nH samples adjacent to the right boundary of the current block ofsize nW×nH, a total of nW samples adjacent to the bottom boundary of thecurrent block and a sample adjacent to the bottom-right of the currentblock.

On the other hand, when the MRL is applied (that is, when the value ofthe MRL index is greater than 0), the neighboring reference samples maybe located on lines 1 to 2 instead of line 0 adjacent to the currentblock on the left/top side, and in this case, the number of theneighboring reference samples may be further increased. Meanwhile, whenthe ISP is applied, the neighboring reference samples may be derived inunits of sub-partitions.

The coding device derives prediction samples by performing intraprediction on the current block S620. The coding device may derive theprediction samples based on the intra prediction mode/type and theneighboring samples. The coding device may derive a reference sampleaccording to an intra prediction mode of the current block amongneighboring reference samples of the current block, and may derive aprediction sample of the current block based on the reference sample.

Meanwhile, when inter prediction is applied, the predictor of theencoding apparatus/decoding apparatus may derive prediction samples byperforming inter prediction in units of blocks. The inter prediction maybe applied when performing the prediction on the current block. That is,the predictor (more specifically, inter predictor) of theencoding/decoding apparatus may derive prediction samples by performingthe inter prediction in units of the block. The inter prediction mayrepresent prediction derived by a method dependent to the data elements(e.g., sample values or motion information) of a picture(s) other thanthe current picture. When the inter prediction is applied to the currentblock, a predicted block (prediction sample array) for the current blockmay be derived based on a reference block (reference sample array)specified by the motion vector on the reference picture indicated by thereference picture index. In this case, in order to reduce an amount ofmotion information transmitted in the inter-prediction mode, the motioninformation of the current block may be predicted in units of a block, asubblock, or a sample based on a correlation of the motion informationbetween the neighboring block and the current block. The motioninformation may include the motion vector and the reference pictureindex. The motion information may further include inter-prediction type(L0 prediction, L1 prediction, Bi prediction, etc.) information. In thecase of applying the inter prediction, the neighboring block may includea spatial neighboring block which is present in the current picture anda temporal neighboring block which is present in the reference picture.A reference picture including the reference block and a referencepicture including the temporal neighboring block may be the same as eachother or different from each other. The temporal neighboring block maybe referred to as a name such as a collocated reference block, acollocated CU (colCU), etc., and the reference picture including thetemporal neighboring block may be referred to as a collocated picture(colPic). For example, a motion information candidate list may beconfigured based on the neighboring blocks of the current block and aflag or index information indicating which candidate is selected (used)may be signaled in order to derive the motion vector and/or referencepicture index of the current block. The inter prediction may beperformed based on various prediction modes and for example, in the caseof a skip mode and a merge mode, the motion information of the currentblock may be the same as the motion information of the selectedneighboring block. In the case of the skip mode, the residual signal maynot be transmitted unlike the merge mode. In the case of a motion vectorprediction (MVP) mode, the motion vector of the selected neighboringblock may be used as a motion vector predictor and a motion vectordifference may be signaled. In this case, the motion vector of thecurrent block may be derived by using a sum of the motion vectorpredictor and the motion vector difference.

The motion information may further include L0 motion information and/orL1 motion information according to the inter-prediction type (L0prediction, L1 prediction, Bi prediction, etc.). A L0-direction motionvector may be referred to as an L0 motion vector or MVL0 and anL1-direction motion vector may be referred to as an L1 motion vector orMVL1. A prediction based on the L0 motion vector may be referred to asan L0 prediction, a prediction based on the L1 motion vector may bereferred to as an L1 prediction, and a prediction based on both the L0motion vector and the L1 motion vector may be referred to as abi-prediction. Here, the L0 motion vector may indicate a motion vectorassociated with a reference picture list L0 and the L1 motion vector mayindicate a motion vector associated with a reference picture list L1.The reference picture list L0 may include pictures prior to the currentpicture in an output order and the reference picture list L1 may includepictures subsequent to the current picture in the output order, as thereference pictures. The prior pictures may be referred to as a forward(reference) picture and the subsequent pictures may be referred to as areverse (reference) picture. The reference picture list L0 may furtherinclude the pictures subsequent to the current picture in the outputorder as the reference pictures. In this case, the prior pictures may befirst indexed in the reference picture list L0 and the subsequentpictures may then be indexed. The reference picture list L1 may furtherinclude the pictures prior to the current picture in the output order asthe reference pictures. In this case, the subsequent pictures may befirst indexed in the reference picture list L1 and the prior picturesmay then be indexed. Here, the output order may correspond to a pictureorder count (POC) order.

A video/image encoding process based on inter prediction mayschematically include, for example, the following.

FIG. 7 illustrates an example of an inter prediction-based video/imageencoding method.

The encoding apparatus performs the inter prediction for the currentblock (S700). The encoding apparatus may derive the inter predictionmode and the motion information of the current block and generate theprediction samples of the current block. Here, an inter prediction modedetermining process, a motion information deriving process, and ageneration process of the prediction samples may be simultaneouslyperformed and any one process may be performed earlier than otherprocess. For example, the inter-prediction unit of the encodingapparatus may include a prediction mode determination unit, a motioninformation derivation unit, and a prediction sample derivation unit,and the prediction mode determination unit may determine the predictionmode for the current block, the motion information derivation unit mayderive the motion information of the current block, and the predictionsample derivation unit may derive the prediction samples of the currentblock. For example, the inter-prediction unit of the encoding apparatusmay search a block similar to the current block in a predetermined area(search area) of reference pictures through motion estimation and derivea reference block in which a difference from the current block isminimum or is equal to or less than a predetermined criterion. Areference picture index indicating a reference picture at which thereference block is positioned may be derived based thereon and a motionvector may be derived based on a difference in location between thereference block and the current block. The encoding apparatus maydetermine a mode applied to the current block among various predictionmodes. The encoding apparatus may compare RD cost for the variousprediction modes and determine an optimal prediction mode for thecurrent block.

For example, when the skip mode or the merge mode is applied to thecurrent block, the encoding apparatus may configure a merging candidatelist to be described below and derive a reference block in which adifference from the current block is minimum or is equal to or less thana predetermined criterion among reference blocks indicated by mergecandidates included in the merging candidate list. In this case, a mergecandidate associated with the derived reference block may be selectedand merge index information indicating the selected merge candidate maybe generated and signaled to the decoding apparatus. The motioninformation of the current block may be derived by using the motioninformation of the selected merge candidate.

As another example, when an (A)MVP mode is applied to the current block,the encoding apparatus may configure an (A)MVP candidate list to bedescribed below and use a motion vector of a selected mvp candidateamong motion vector predictor (mvp) candidates included in the (A)MVPcandidate list as the mvp of the current block. In this case, forexample, the motion vector indicating the reference block derived by themotion estimation may be used as the motion vector of the current blockand an mvp candidate having a motion vector with a smallest differencefrom the motion vector of the current block among the mvp candidates maybecome the selected mvp candidate. A motion vector difference (MVD)which is a difference obtained by subtracting the mvp from the motionvector of the current block may be derived. In this case, theinformation on the MVD may be signaled to the decoding apparatus.Further, when the (A)MVP mode is applied, the value of the referencepicture index may be configured as reference picture index informationand separately signaled to the decoding apparatus.

The encoding apparatus may derive the residual samples based on thepredicted samples (S710). The encoding apparatus may derive the residualsamples by comparing original samples and the prediction samples of thecurrent block.

The encoding apparatus encodes image information including predictioninformation and residual information (S720). The encoding apparatus mayoutput the encoded image information in the form of a bitstream. Theprediction information may include information on prediction modeinformation (e.g., skip flag, merge flag or mode index, etc.) andinformation on motion information as information related to theprediction procedure. The information on the motion information mayinclude candidate selection information (e.g., merge index, mvp flag ormvp index) which is information for deriving the motion vector. Further,the information on the motion information may include the information onthe MVD and/or the reference picture index information. Further, theinformation on the motion information may include information indicatingwhether to apply the L0 prediction, the L1 prediction, or thebi-prediction. The residual information is information on the residualsamples. The residual information may include information on quantizedtransform coefficients for the residual samples.

An output bitstream may be stored in a (digital) storage medium andtransferred to the decoding apparatus or transferred to the decodingapparatus via the network.

Meanwhile, as described above, the encoding apparatus may generate areconstructed picture (including reconstructed samples and reconstructedblocks) based on the reference samples and the residual samples. This isto derive the same prediction result as that performed by the decodingapparatus, and as a result, coding efficiency may be increased.Accordingly, the encoding apparatus may store the reconstruction picture(or reconstruction samples or reconstruction blocks) in the memory andutilize the reconstruction picture as the reference picture. The in-loopfiltering process may be further applied to the reconstruction pictureas described above.

A video/image decoding process based on inter prediction mayschematically include, for example, the following.

FIG. 8 illustrates an example of an inter prediction-based video/imagedecoding method.

Referring to FIG. 8 , the decoding apparatus may perform an operationcorresponding to the operation performed by the encoding apparatus. Thedecoding apparatus may perform the prediction for the current blockbased on received prediction information and derive the predictionsamples.

Specifically, the decoding apparatus may determine the prediction modefor the current block based on the received prediction information(S800). The decoding apparatus may determine which inter prediction modeis applied to the current block based on the prediction mode informationin the prediction information.

For example, it may be determined whether the merge mode or the (A)MVPmode is applied to the current block based on the merge flag.Alternatively, one of various inter prediction mode candidates may beselected based on the mode index. The inter prediction mode candidatesmay include a skip mode, a merge mode, and/or an (A)MVP mode or mayinclude various inter prediction modes to be described below.

The decoding apparatus derives the motion information of the currentblock based on the determined inter prediction mode (S810). For example,when the skip mode or the merge mode is applied to the current block,the decoding apparatus may configure the merge candidate list to bedescribed below and select one merge candidate among the mergecandidates included in the merge candidate list. Here, the selection maybe performed based on the selection information (merge index). Themotion information of the current block may be derived by using themotion information of the selected merge candidate. The motioninformation of the selected merge candidate may be used as the motioninformation of the current block.

As another example, when an (A)MVP mode is applied to the current block,the decoding apparatus may configure an (A)MVP candidate list to bedescribed below and use a motion vector of a selected mvp candidateamong motion vector predictor (mvp) candidates included in the (A)MVPcandidate list as the mvp of the current block. Here, the selection maybe performed based on the selection information (mvp flag or mvp index).In this case, the MVD of the current block may be derived based on theinformation on the MVD, and the motion vector of the current block maybe derived based on the mvp of the current block and the MVD. Further,the reference picture index of the current block may be derived based onthe reference picture index information. The picture indicated by thereference picture index in the reference picture list for the currentblock may be derived as the reference picture referred for the interprediction of the current block.

Meanwhile, as described below, the motion information of the currentblock may be derived without a candidate list configuration and in thiscase, the motion information of the current block may be derivedaccording to a procedure disclosed in the prediction mode. In this case,the candidate list configuration may be omitted.

The decoding apparatus may generate the prediction samples for thecurrent block based on the motion information of the current block(S820). In this case, the reference picture may be derived based on thereference picture index of the current block and the prediction samplesof the current block may be derived by using the samples of thereference block indicated by the motion vector of the current block onthe reference picture. In this case, in some cases, a predicted samplefiltering procedure for all or some of the prediction samples of thecurrent block may be further performed.

For example, the inter-prediction unit of the decoding apparatus mayinclude a prediction mode determination unit, a motion informationderivation unit, and a prediction sample derivation unit, and theprediction mode determination unit may determine the prediction mode forthe current block based on the received prediction mode information, themotion information derivation unit may derive the motion information(the motion vector and/or reference picture index) of the current blockbased on the information on the received motion information, and theprediction sample derivation unit may derive the predicted samples ofthe current block.

The decoding apparatus generates the residual samples for the currentblock based on the received residual information (S830). The decodingapparatus may generate the reconstruction samples for the current blockbased on the prediction samples and the residual samples and generatethe reconstruction picture based on the generated reconstruction samples(S840). Thereafter, the in-loop filtering procedure may be furtherapplied to the reconstruction picture as described above.

FIG. 9 schematically shows an inter prediction procedure.

Referring to FIG. 9 , as described above, the inter prediction processmay include an inter prediction mode determination step, a motioninformation derivation step according to the determined prediction mode,and a prediction processing (prediction sample generation) step based onthe derived motion information. The inter prediction process may beperformed by the encoding apparatus and the decoding apparatus asdescribed above. In this document, a coding device may include theencoding apparatus and/or the decoding apparatus.

Referring to FIG. 9 , the coding apparatus determines an interprediction mode for the current block (S900). Various inter predictionmodes may be used for the prediction of the current block in thepicture. For example, various modes, such as a merge mode, a skip mode,a motion vector prediction (MVP) mode, an affine mode, a subblock mergemode, a merge with MVD (MMVD) mode, and a historical motion vectorprediction (HMVP) mode may be used. A decoder side motion vectorrefinement (DMVR) mode, an adaptive motion vector resolution (AMVR)mode, a bi-prediction with CU-level weight (BCW), a bi-directionaloptical flow (BDOF), and the like may be further used as additionalmodes. The affine mode may also be referred to as an affine motionprediction mode. The MVP mode may also be referred to as an advancedmotion vector prediction (AMVP) mode. In the present document, somemodes and/or motion information candidates derived by some modes mayalso be included in one of motion information-related candidates inother modes. For example, the HMVP candidate may be added to the mergecandidate of the merge/skip modes, or also be added to an mvp candidateof the MVP mode. If the HMVP candidate is used as the motion informationcandidate of the merge mode or the skip mode, the HMVP candidate may bereferred to as the HMVP merge candidate.

The prediction mode information indicating the inter prediction mode ofthe current block may be signaled from the encoding apparatus to thedecoding apparatus. In this case, the prediction mode information may beincluded in the bitstream and received by the decoding apparatus. Theprediction mode information may include index information indicating oneof multiple candidate modes. Alternatively, the inter prediction modemay be indicated through a hierarchical signaling of flag information.In this case, the prediction mode information may include one or moreflags. For example, whether to apply the skip mode may be indicated bysignaling a skip flag, whether to apply the merge mode may be indicatedby signaling a merge flag when the skip mode is not applied, and it isindicated that the MVP mode is applied or a flag for additionaldistinguishing may be further signaled when the merge mode is notapplied. The affine mode may be signaled as an independent mode orsignaled as a dependent mode on the merge mode or the MVP mode. Forexample, the affine mode may include an affine merge mode and an affineMVP mode.

The coding apparatus derives motion information for the current block(S910). Motion information derivation may be derived based on the interprediction mode.

The coding apparatus may perform inter prediction using motioninformation of the current block. The encoding apparatus may deriveoptimal motion information for the current block through a motionestimation procedure. For example, the encoding apparatus may search asimilar reference block having a high correlation in units of afractional pixel within a predetermined search range in the referencepicture by using an original block in an original picture for thecurrent block and derive the motion information through the searchedreference block. The similarity of the block may be derived based on adifference of phase based sample values. For example, the similarity ofthe block may be calculated based on a sum of absolute differences (SAD)between the current block (or a template of the current block) and thereference block (or the template of the reference block). In this case,the motion information may be derived based on a reference block havinga smallest SAD in a search area. The derived motion information may besignaled to the decoding apparatus according to various methods based onthe inter prediction mode.

The coding apparatus performs inter prediction based on motioninformation for the current block (S920). The coding apparatus mayderive prediction sample(s) for the current block based on the motioninformation. A current block including prediction samples may bereferred to as a predicted block.

Meanwhile, as described above, the encoding apparatus may performvarious encoding methods such as exponential Golomb, context-adaptivevariable length coding (CAVLC), and context-adaptive binary arithmeticcoding (CABAC). In addition, the decoding apparatus may decodeinformation in a bitstream based on a coding method such as exponentialGolomb coding, CAVLC or CABAC, and output a value of a syntax elementrequired for image reconstruction and quantized values of transformcoefficients related to residuals.

For example, the coding methods described above may be performed asdescribed below.

FIG. 10 exemplarily shows context-adaptive binary arithmetic coding(CABAC) for encoding a syntax element. For example, in the CABACencoding process, when an input signal is a syntax element, rather thana binary value, the encoding apparatus may convert the input signal intoa binary value by binarizing the value of the input signal. In addition,when the input signal is already a binary value (i.e., when the value ofthe input signal is a binary value), binarization may not be performedand may be bypassed. Here, each binary number 0 or 1 constituting abinary value may be referred to as a bin. For example, if a binarystring after binarization is 110, each of 1, 1, and 0 is called one bin.The bin(s) for one syntax element may indicate a value of the syntaxelement.

Thereafter, the binarized bins of the syntax element may be input to aregular coding engine or a bypass coding engine. The regular codingengine of the encoding apparatus may allocate a context model reflectinga probability value to the corresponding bin, and may encode thecorresponding bin based on the allocated context model. The regularcoding engine of the encoding apparatus may update a context model foreach bin after performing encoding on each bin. A bin encoded asdescribed above may be referred to as a context-coded bin.

Meanwhile, when the binarized bins of the syntax element are input tothe bypass coding engine, they may be coded as follows. For example, thebypass coding engine of the encoding apparatus omits a procedure ofestimating a probability with respect to an input bin and a procedure ofupdating a probability model applied to the bin after encoding. Whenbypass encoding is applied, the encoding apparatus may encode the inputbin by applying a uniform probability distribution instead of allocatinga context model, thereby improving an encoding rate. The bin encoded asdescribed above may be referred to as a bypass bin.

Entropy decoding may represent a process of performing the same processas the entropy encoding described above in reverse order.

For example, when a syntax element is decoded based on a context model,the decoding apparatus may receive a bin corresponding to the syntaxelement through a bitstream, determine a context model using the syntaxelement and decoding information of a decoding target block or aneighbor block or information of a symbol/bin decoded in a previousstage, predict an occurrence probability of the received bin accordingto the determined context model, and perform an arithmetic decoding onthe bin to derive a value of the syntax element. Thereafter, a contextmodel of a bin which is decoded next may be updated with the determinedcontext model.

Also, for example, when a syntax element is bypass-decoded, the decodingapparatus may receive a bin corresponding to the syntax element througha bitstream, and decode the input bin by applying a uniform probabilitydistribution. In this case, the procedure of the decoding apparatus forderiving the context model of the syntax element and the procedure ofupdating the context model applied to the bin after decoding may beomitted.

As described above, residual samples may be derived as quantizedtransform coefficients through transform and quantization processes. Thequantized transform coefficients may also be referred to as transformcoefficients. In this case, the transform coefficients in a block may besignaled in the form of residual information. The residual informationmay include a residual coding syntax. That is, the encoding apparatusmay configure a residual coding syntax with residual information, encodethe same, and output it in the form of a bitstream, and the decodingapparatus may decode the residual coding syntax from the bitstream andderive residual (quantized) transform coefficients. The residual codingsyntax may include syntax elements representing whether transform wasapplied to the corresponding block, a location of a last effectivetransform coefficient in the block, whether an effective transformcoefficient exists in the subblock, a size/sign of the effectivetransform coefficient, and the like, as will be described later.

For example, syntax elements related to residual data encoding/decodingmay be represented as shown in the following table.

TABLE 1 Descriptor transform_unit( x0, y0, tbWidth, tbHeight, treeType,subTuIndex, chType ) {  if( IntraSubPartitionsSplitType != ISP_NO_SPLIT&&    treeType = = SINGLE_TREE && subTuIndex = = NumIntraSubPartiti ons− 1 ) {   xC = CbPosX[ chType ][ x0 ][ y0 ]   yC = CbPosY[ chType ][ x0][ y0 ]   wC = CbWidth[ chType ][ x0 ][ y0 ] / SubWidthC   hC =CbHeight[ chType ][ x0 ][ y0 ] / SubHeightC  } else {   xC = x0   yC =y0   wC = tbWidth / SubWidthC   hC = tbHeight / SubHeightC  } chromaAvailable = treeType != DUAL_TREE_LUMA && sps_chroma_form at_idc!= 0 &&   ( IntraSubPartitionsSplitType = = ISP_NO_SPLIT | |   (IntraSubPartitionsSplitType != ISP_NO_SPLIT &&   subTuIndex = =NumIntraSubPartitions − 1 ) )  if( ( treeType = = SINGLE_TREE | |treeType = = DUAL_TREE_CHROM A ) &&    sps_chroma_format_idc != 0 &&   ( ( IntraSubPartitionsSplitType = = ISP_NO_SPLIT && !( cu_sbt_flag &&   ( ( subTuIndex = = 0 && cu_sbt_pos_flag ) | |    ( subTuIndex = = 1&& !cu_sbt_pos_flag ) ) ) ) | |    ( IntraSubPartitionsSplitType !=ISP_NO_SPLIT &&    ( subTuIndex = = NumIntraSubPartitions − 1 ) ) ) ) {  tu_cb_coded_flag[ xC ][ yC ] ae(v)   tu_cr_coded_flag[ xC ][ yC ]ae(v)  }  if( treeType = = SINGLE_TREE | | treeType = = DUAL_TREE_LUMA ){   if( ( IntraSubPartitionsSplitType = = ISP_NO_SPLIT && !( cu_sbt_flag& &     ( ( subTuIndex = = 0 && cu_sbt_pos_flag ) | |     ( subTuIndex == 1 && !cu_sbt_pos_flag ) ) ) &&     ( ( CuPredMode[ chType ][ x0 ][ y0] = = MODE_INTRA &&     !cu_act_enabled_flag[ x0 ][ y0 ] ) | |     (chromaAvailable && ( tu_cb_coded_flag[ xC ][ yC ] | |    tu_cr_coded_flag[ xC ][ yC ] ) ) | |     CbWidth[ chType ][ x0 ][ y0] > MaxTbSizeY | |     CbHeight[ chType ][ x0 ][ y0 ] > MaxTbSizeY ) ) ||     ( IntraSubPartitionsSplitType != ISP_NO_SPLIT &&     ( subTuIndex< NumIntraSubPartitions − 1 | | !InferTuCbfLuma ) ) )   tu_y_coded_flag[ x0 ][ y0 ] ae(v)   if(IntraSubPartitionsSplitType !=ISP_NO_SPLIT )    InferTuCbfLuma = InferTuCbfLuma && !tu_y_coded_flag[x0 ][ y0 ]  }  if( ( CbWidth[ chType ][ x0 ][ y0 ] > 64 | | CbHeight[chType ][ x0 ][ y 0 ] > 64 | |    tu_y_coded_flag[ x0 ][ y0 ] | | (chromaAvailable && ( tu_cb_coded_flag [ xC ][ yC ] | |   tu_cr_coded_flag[ xC ][ yC ] ) ) && treeType != DUAL_TREE_CHRO MA &&   pps_cu_qp_delta_enabled_flag && !IsCuQpDeltaCoded ) {  cu_qp_delta_abs ae(v)   if( cu_qp_delta_abs )    cu_qp_delta_sign_flagae(v)  }  if( ( CbWidth[ chType ][ x0 ][ y0 ] > 64 | | CbHeight[ chType][ x0 ][ y 0 ] > 64 | |    ( chromaAvailable && ( tu_cb_coded_flag[ xC][ yC ] | |    tu_cr_coded_flag[ xC ][ yC ] ) ) ) &&    treeType !=DUAL_TREE_LUMA && sh_cu_chroma_qp_offset_enable d_flag &&   !IsCuChromaQpOffsetCoded ) {   cu_chroma_qp_offset_flag ae(v)   if(cu_chroma_qp_offset_flag && pps_chroma_qp_offset_list_len_minus1 > 0 )   cu_chroma_qp_offset_idx ae(v) }  if( sps_joint_cbcr_enabled_flag && (( CuPredMode[ chType ][ x0 ][ y0 ] = = MODE_INTRA    && (tu_cb_coded_flag[ xC ][ yC ] | | tu_cr_coded_flag[ xC ][ yC ] ) ) | |   ( tu_cb_coded_flag[ xC ][ yC ] && tu_cr_coded_flag[ xC ][ yC ] ) ) &&   chromaAvailable )   tu_joint_cbcr_residual_flag[ xC ][ yC ] ae(v) if( tu_y_coded_flag[ x0 ][ y0 ] && treeType != DUAL_TREE_CHROMA ) {  if( sps_transform_skip_enabled_flag && !BdpcmFlag[ x0 ][ y0 ][ 0 ] &&    tbWidth <= MaxTsSize && tbHeight <= MaxTsSize &&     (IntraSubPartitionsSplitType = = ISP_NO_SPLIT ) && !cu_sbt_flag )   transform_skip_flag[ x0 ][ y0 ][ 0 ] ae(v)   if(!transform_skip_flag[ x0 ][ y0 ][ 0 ] | |sh_ts_residual_coding_disabled_fla g )    residual_coding( x0, y0, Log2(tbWidth ), Log2( tbHeight ), 0 )   else    residual_ts_coding( x0, y0,Log2( tbWidth ), Log2( tbHeight ), 0 )  }  if( tu_cb_coded_flag[ xC ][yC ] && treeType != DUAL_TREE_LUMA ) {   if(sps_transform_skip_enabled_flag && !BdpcmFlag[ x0 ][ y0 ][ 1 ] &&     wC<= MaxTsSize && hC <= MaxTsSize && !cu_sbt_flag )   transform_skip_flag[ xC ][ yC ][ 1 ] ae(v)   if(!transform_skip_flag[ xC ][ yC ][ 1 ] | |sh_ts_residual_coding_disabled_fl ag )    residual_coding( xC, yC, Log2(wC ), Log2( hC ), 1 )   else    residual_ts_coding( xC, yC, Log2( wC ),Log2( hC ), 1 )  }  if( tu_cr_coded_flag[ xC ][ yC ] && treeType !=DUAL_TREE_LUMA &&    !( tu_cb_coded_flag[ xC ][ yC ] &&tu_joint_cbcr_residual_flag[ xC ][ y C ] ) ) {   if(sps_transform_skip_enabled_flag && !BdpcmFlag[ x0 ][ y0 ][ 2 ] &&     wC<= MaxTsSize && hC <= MaxTsSize && !cu_sbt_flag )   transform_skip_flag[ xC ][ yC ][ 2 ] ae(v)   if(!transform_skip_flag[ xC ][ yC ][ 2 ] | |sh_ts_residual_coding_disabled_fl ag )    residual_coding( xC, yC, Log2(wC ), Log2( hC ), 2 )   else    residual_ts_coding( xC, yC, Log2( wC ),Log2( hC ), 2 )  } }

transform_skip_flag indicates whether transform is skipped in anassociated block. The transform_skip_flag may be a syntax element of atransform skip flag. The associated block may be a coding block (CB) ora transform block (TB). Regarding transform (and quantization) andresidual coding procedures, CB and TB may be used interchangeably. Forexample, as described above, residual samples may be derived for CB, and(quantized) transform coefficients may be derived through transform andquantization for the residual samples, and through the residual codingprocedure, information (e.g., syntax elements) efficiently indicating aposition, magnitude, sign, etc. of the (quantized) transformcoefficients may be generated and signaled. The quantized transformcoefficients may simply be called transform coefficients. In general,when the CB is not larger than a maximum TB, a size of the CB may be thesame as a size of the TB, and in this case, a target block to betransformed (and quantized) and residual coded may be called a CB or aTB. Meanwhile, when the CB is greater than the maximum TB, a targetblock to be transformed (and quantized) and residual coded may be calleda TB. Hereinafter, it will be described that syntax elements related toresidual coding are signaled in units of transform blocks (TBs) but thisis an example and the TB may be used interchangeably with coding blocks(CBs as described above.

Meanwhile, syntax elements which are signaled after the transform skipflag is signaled may be the same as the syntax elements disclosed inTable 2 and/or Table 3 below, and detailed descriptions on the syntaxelements are described below.

TABLE 2 Descriptor residual_coding( x0, y0, log2TbWidth, log2TbHeight,cIdx ) {  if( sps_mts_enabled_flag && cu_sbt_flag && cIdx = = 0 &&   log2TbWidth = = 5 && log2TbHeight < 6 )   log2ZoTbWidth = 4  else  log2ZoTbWidth = Min( log2TbWidth, 5 )  if( sps_mts_enabled_flag &&cu_sbt_flag && cIdx = = 0 &&    log2TbWidth < 6 && log2TbHeight = = 5 )  log2ZoTbHeight = 4  else   log2ZoTbHeight = Min( log2TbHeight, 5 ) if( log2TbWidth > 0 )   last_sig_coeff_x_prefix ae(v)  if(log2TbHeight > 0 )   last_sig_coeff_y_prefix ae(v)  if(last_sig_coeff_x_prefix > 3 )   last_sig_coeff_x_suffix ae(v)  if(last_sig_coeff_y_prefix > 3 )   last_sig_coeff_y_suffix ae(v) log2TbWidth = log2ZoTbWidth  log2TbHeight = log2ZoTbHeight remBinsPass1 = ( ( 1 << ( log2TbWidth + log2TbHeight ) ) * 7 ) >> 2 log2SbW = ( Min( log2TbWidth, log2TbHeight ) < 2 ? 1 : 2 )  log2SbH =log2SbW  if( log2TbWidth + log2TbHeight > 3 )   if( log2TbWidth < 2 ) {   log2SbW = log2TbWidth    log2SbH = 4 − log2SbW   } else if(log2TbHeight < 2 ) {    log2SbH = log2TbHeight    log2SbW = 4 − log2SbH  }  numSbCoeff = 1 << ( log2SbW + log2SbH )  lastScanPos = numSbCoeff lastSubBlock = ( 1 << ( log2TbWidth + log2TbHeight − ( log2SbW + log2SbH ) ) ) − 1  do {   if( lastScanPos = = 0 ) {    lastScanPos =numSbCoeff    lastSubBlock− −   }   lastScanPos− −   xS = DiagScanOrder[log2TbWidth − log2SbW ][ log2TbHeight − log2SbH ]         [ lastSubBlock][ 0 ]   yS = DiagScanOrder[ log2TbWidth − log2SbW ][ log2TbHeight −log2SbH ]         [ lastSubBlock ][ 1 ]   xC = ( xS << log2SbW ) +DiagScanOrder[ log2SbW ][ log2SbH ][ lastScan Pos ][ 0 ]   yC = ( yS <<log2SbH ) + DiagScanOrder[ log2SbW ][ log2SbH ][ lastScan Pos ][ 1 ]  }while( ( xC != LastSignificantCoeffX ) | | ( yC != LastSignificantCoeffY) )  if( lastSubBlock = = 0 && log2TbWidth >= 2 && log2TbHeight >= 2 & &   !transform_skip_flag[ x0 ][ y0 ][ cIdx ] && lastScanPos > 0 )  LfnstDcOnly = 0  if( ( lastSubBlock > 0 && log2TbWidth >= 2 &&log2TbHeight >= 2 ) | |    ( lastScanPos > 7 && ( log2TbWidth = = 2 | |log2TbWidth = = 3 ) & &    log2TbWidth = = log2TbHeight ) )  LfnstZeroOutSigCoeffFlag = 0  if( ( lastSubBlock > 0 | | lastScanPos >0 ) && cIdx = = 0 )   MtsDcOnly = 0  QState = 0  for( i = lastSubBlock;i >= 0; i− − ) {   startQStateSb = QState   xS = DiagScanOrder[log2TbWidth − log2SbW ][ log2TbHeight − log2SbH ]         [ i ][ 0 ]  yS = DiagScanOrder[ log2TbWidth − log2SbW ][ log2TbHeight − log2SbH ]        [ i ][ 1 ]   inferSbDcSigCoeffFlag = 0   if( i < lastSubBlock &&i > 0 ) {F    sb_coded_flag[ xS ][ yS ] ae(v)    inferSbDcSigCoeffFlag =1   }   if( sb_coded_flag[ xS ][ yS ] && ( xS > 3 | | yS > 3 ) && cIdx == 0 )    MtsZeroOutSigCoeffFlag = 0   firstSigScanPosSb = numSbCoeff  lastSigScanPosSb = −1   firstPosMode0 = ( i = = lastSubBlock ?lastScanPos : numSbCoeff − 1 )   firstPosMode1 = firstPosMode0   for( n= firstPosMode0; n >= 0 && remBinsPass1 >= 4; n− − ) {    xC = ( xS <<log2SbW ) + DiagScanOrder[ log2SbW ][ log2SbH ][ n ] [ 0 ]    yC = ( yS<< log2SbH ) + DiagScanOrder[ log2SbW ][ log2SbH ][ n ] [ 1 ]    if(sb_coded_flag[ xS ][ yS ] && ( n > 0 | | !inferSbDcSigCoeffFlag ) & &     ( xC != LastSignificantCoeffX | | yC != LastSignificantCoeffY ) ) {    sig_coeff_flag[ xC ][ yC ] ae(v)     remBinsPass1− −     if(sig_coeff_flag[ xC ][ yC ] )      inferSbDcSigCoeffFlag = 0    }    if(sig_coeff_flag[ xC ][ yC ] ) {     abs_level_gtx_flag[ n ][ 0 ] ae(v)    remBinsPass1− −     if( abs_level_gtx_flag[ n ][ 0 ] ) {     par_level_flag[ n ] ae(v)      remBinsPass1− −     abs_level_gtx_flag[ n ][ 1 ] ae(v)      remBinsPass1− −     }    if( lastSigScanPosSb = = −1 )      lastSigScanPosSb = n    firstSigScanPosSb = n    }    AbsLevelPass1[ xC ][ yC ] =sig_coeff_flag[ xC ][ yC ] + par_level_flag [ n ] +          abs_level_gtx_flag[ n ][ 0 ] + 2 * abs_level_gtx_flag[ n ] [ 1]    if( sh_dep_quant_used_flag )     QState = QStateTransTable[ QState][ AbsLevelPass1[ xC ][ yC ] & 1 ]    firstPosMode1 = n − 1   }   for( n= firstPosMode0; n > firstPosMode1; n− − ) {    xC = ( xS << log2SbW ) +DiagScanOrder[ log2SbW ][ log2SbH ][ n ] [ 0 ]    yC = ( yS << log2SbH) + DiagScanOrder[ log2SbW ][ log2SbH ][ n ] [ 1 ]    if(abs_level_gtx_flag[ n ][ 1 ] )     abs_remainder[ n ] ae(v)    AbsLevel[xC ][ yC ] = AbsLevelPass1[ xC ][ yC ] +2 * abs_remainder[ n ]   }  for( n = firstPosMode1; n >= 0; n− − ) {    xC = ( xS << log2SbW ) +DiagScanOrder[ log2SbW ][ log2SbH ][ n ] [ 0 ]    yC = ( yS << log2SbH) + DiagScanOrder[ log2SbW ][ log2SbH ][ n ] [ 1 ]    if( sb_coded_flag[xS ][ yS ] )     dec_abs_level[ n ] ae(v)    if( AbsLevel[ xC ][ yC ] >0 ) {     if( lastSigScanPosSb = = −1 )      lastSigScanPosSb = n    firstSigScanPosSb = n    }    if( sh_dep_quant_used_flag )    QState = QStateTransTable[ QState ][ AbsLevel[ xC ][ yC ] & 1 ]   }  if( sh_dep_quant_used_flag | | !sh_sign_data_hiding_used_flag )   signHidden = 0   else    signHidden = ( lastSigScanPosSb −firstSigScanPosSb > 3 ? 1 : 0 )   for( n = numSbCoeff − 1; n >= 0; n− −) {    xC = ( xS << log2SbW ) + DiagScanOrder[ log2SbW ][ log2SbH ][ n ][ 0 ]    yC = ( yS << log2SbH ) + DiagScanOrder[ log2SbW ][ log2SbH ][ n] [ 1 ]    if( ( AbsLevel[ xC ][ yC ] > 0 ) &&     ( !signHidden | | ( n!= firstSigScanPosSb ) ) )     coeff_sign_flag[ n ] ae(v)   }   if(sh_dep_quant_used_flag ) {    QState = startQStateSb    for( n =numSbCoeff − 1; n >= 0; n− − ) {     xC = ( xS << log2SbW ) +DiagScanOrder[ log2SbW ][ log2SbH ][ n ] [ 0 ]     yC = ( yS << log2SbH) + DiagScanOrder[ log2SbW ][ log2SbH ][ n ] [ 1 ]     if( AbsLevel[ xC][ yC ] > 0 )      TransCoeffLevel[ x0 ][ y0 ][ cIdx ][ xC ][ yC ] =       ( 2 * AbsLevel[ xC ][ yC ] − ( QState > 1 ? 1 : 0 ) ) *        (1 − 2 * coeff_sign_flag[ n ] )     QState = QStateTransTable[ QState ][AbsLevel[ xC ][ yC ] & 1 ]   } else {    sumAbsLevel = 0    for( n =numSbCoeff − 1; n >= 0; n− − ) {     xC = ( xS << log2SbW ) +DiagScanOrder[ log2SbW ][ log2SbH ][ n ] [ 0 ]     yC = ( yS << log2SbH) + DiagScanOrder[ log2SbW ][ log2SbH ][ n ] [ 1 ]     if( AbsLevel[ xC][ yC ] > 0 ) {      TransCoeffLevel[ x0 ][ y0 ][ cIdx ][ xC ][ yC ] =       AbsLevel[ xC ][ yC ] * ( 1 − 2 * coeff_sign_flag[ n ] )      if(signHidden ) {       sumAbsLevel += AbsLevel[ xC ][ yC ]       if( ( n == firstSigScanPosSb ) && ( sumAbsLevel % 2 ) = = 1 ) )       TransCoeffLevel[ x0 ][ y0 ][ cIdx ][ xC ][ yC ] =         −TransCoeffLevel[ x0 ][ y0 ][ cIdx ][ xC ][ yC ]      }     }   }   }  } }

TABLE 3 Descriptor residual_ts_coding( x0, y0, log2TbWidth,log2TbHeight, cIdx ) {  log2SbW = ( Min( log2TbWidth, log2TbHeight ) < 2? 1 : 2 )  log2SbH = log2SbW  if( log2TbWidth + log2TbHeight > 3 )   if(log2TbWidth < 2 ) {    log2SbW = log2TbWidth    log2SbH = 4 − log2SbW  } else if( log2TbHeight < 2 ) {    log2SbH = log2TbHeight    log2SbW =4 − log2SbH   }  numSbCoeff = 1 << ( log2SbW + log2SbH )  lastSubBlock =( 1 << ( log2TbWidth + log2TbHeight − ( log2SbW + log2Sb H ) ) ) − 1 inferSbCbf = 1  RemCcbs = ( ( 1 << ( log2TbWidth + log2TbHeight ) ) * 7) >> 2  for( i =0; i <= lastSubBlock; i++ ) {   xS = DiagScanOrder[log2TbWidth − log2SbW ][ log2TbHeight − log2SbH ] [ i ][ 0 ]   yS =DiagScanOrder[ log2TbWidth − log2SbW ][ log2TbHeight − log2SbH ] [ i ][1 ]   if( i != lastSubBlock | | !inferSbCbf )    sb_coded_flag[ xS ][ yS] ae(v)   if( sb_coded_flag[ xS ][ yS ] && i < lastSubBlock )   inferSbCbf = 0  /* First scan pass */   inferSbSigCoeffFlag = 1  lastScanPosPass1 = −1   for( n = 0; n <= numSbCoeff − 1 && RemCcbs >=4; n++ ) {    xC = ( xS << log2SbW ) + DiagScanOrder[ log2SbW ][ log2SbH][ n ] [ 0 ]    yC = ( yS << log2SbH ) + DiagScanOrder[ log2SbW ][log2SbH ][ n ] [ 1 ]    lastScanPosPass1 = n    if( sb_coded_flag[ xS ][yS ] &&      ( n != numSbCoeff − 1 | | !inferSbSigCoeffFlag ) ) {    sig_coeff_flag[ xC ][ yC ] ae(v)     RemCcbs− −     if(sig_coeff_flag[ xC ][ yC ] )      inferSbSigCoeffFlag = 0    }   CoeffSignLevel[ xC ][ yC ] = 0    if( sig_coeff_flag[ xC ][ yC ] ) {    coeff_sign_flag[ n ] ae(v)     RemCcbs− −     CoeffSignLevel[ xC ][yC ] = ( coeff_sign_flag[ n ] > 0 ? −1 : 1 )     abs_level_gtx_flag[ n][ 0 ] ae(v)     RemCcbs− −     if( abs_level_gtx_flag[ n ][ 0 ] ) {     par_level_flag[ n ] ae(v)      RemCcbs− −     }    }   AbsLevelPass1[ xC ][ yC ] =      sig_coeff_flag[ xC ][ yC ] +par_level_flag[ n ] + abs_level_gtx_flag [ n ][ 0 ]   }  /* Greater thanX scan pass (numGtXFlags=5) */   lastScanPosPass2 = −1   for( n = 0; n<= numSbCoeff − 1 && RemCcbs >= 4; n++ ) {    xC = ( xS << log2SbW ) +DiagScanOrder[ log2SbW ][ log2SbH ][ n ] [ 0 ]    yC = ( yS << log2SbH) + DiagScanOrder[ log2SbW ][ log2SbH ][ n ] [ 1 ]    AbsLevelPass2[ xC][ yC ] = AbsLevelPass1[ xC ][ yC ]    for( j = 1; j < 5; j++ ) {    if( abs_level_gtx_flag[ n ][ j − 1 ] ) {      abs_level_gtx_flag[ n][ j ] ae(v)      RemCcbs− −     }     AbsLevelPass2[ xC ][ yC ] += 2 *abs_level_gtx_flag[ n ][ j ]    }    lastScanPosPass2 = n   }  /*remainder scan pass */   for( n = 0; n <= numSbCoeff − 1; n++ ) {    xC= ( xS << log2SbW ) + DiagScanOrder[ log2SbW ][ log2SbH ][ n ] [ 0 ]   yC = ( yS << log2SbH ) + DiagScanOrder[ log2SbW ][ log2SbH ][ n ] [ 1]    if( ( n <= lastScanPosPass2 && AbsLevelPass2[ xC ][ yC ] >= 10 ) ||      ( n > lastScanPosPass2 && n <= lastScanPosPass1 &&     AbsLevelPass1[ xC ][ yC ] >= 2 ) | |      ( n > lastScanPosPass1 &&sb_coded_flag[ xS ][ yS ] ) )     abs_remainder[ n ] ae(v)    if( n <=lastScanPosPass2 )     AbsLevel[ xC ][ yC ] = AbsLevelPass2[ xC ][ yC] + 2 * abs_remainder [ n ]    else if(n <= lastScanPosPass1 )    AbsLevel[ xC ][ yC ] = AbsLevelPass1[ xC ][ yC ] + 2 * abs_remainder[ n ]    else { /* bypass */     AbsLevel[ xC ][ yC ] = abs_remainder[ n]     if( abs_remainder[ n ] )      coeff_sign_flag[ n ] ae(v)    }   if( BdpcmFlag[ x0 ][ y0 ][ cIdx ] = = 0 && n <= lastScanPosPass1 ) {    absLeftCoeff = xC > 0 ? AbsLevel[ xC − 1 ][ yC ] ) : 0    absAboveCoeff = yC > 0 ? AbsLevel[ xC ][ yC − 1 ] ) : 0    predCoeff = Max( absLeftCoeff, absAboveCoeff )     if( AbsLevel[ xC][ yC ] = = 1 && predCoeff > 0 )      AbsLevel[ xC ][ yC ] = predCoeff    else if( AbsLevel[ xC ][ yC ] > 0 && AbsLevel[ xC ][ yC ] <= predCoeff )      AbsLevel[ xC ][ yC ]− −    }    TransCoeffLevel[ x0 ][ y0 ][cIdx ][ xC ][ yC ] = ( 1 − 2 * coeff_sign_flag [ n ] ) *      AbsLevel[xC ][ yC ]   }  } }

According to the present embodiment, as shown in Table 1, residualcoding may be divided according to a value of the syntax elementtransform_skip_flag of the transform skip flag. That is, a differentsyntax element may be used for residual coding based on the value of thetransform skip flag (based on whether the transform is skipped).Residual coding used when the transform skip is not applied (that is,when the transform is applied) may be called regular residual coding(RRC), and residual coding used when the transform skip is applied (thatis, when the transform is not applied) may be called transform skipresidual coding (TSRC). Also, the regular residual coding may bereferred to as general residual coding. Also, the regular residualcoding may be referred to as a regular residual coding syntax structure,and the transform skip residual coding may be referred to as a transformskip residual coding syntax structure. Table 2 above may show a syntaxelement of residual coding when a value of transform_skip_flag is 0,that is, when the transform is applied, and Table 3 above may show asyntax element of residual coding when the value of transform_skip_flagis 1, that is, when the transform is not applied.

Specifically, for example, the transform skip flag indicating whether toskip the transform of the transform block may be parsed, and whether thetransform skip flag is 1 may be determined. If the value of thetransform skip flag is 0, as shown in Table 2, syntax elementslast_sig_coeff_x_prefix, last_sig_coeff_y_prefix,last_sig_coeff_x_suffix, last_sig_coeff_y_suffix, sb_coded_flag,sig_coeff_flag, abs_level_gtx_flag, par_level_flag, abs_remainder,coeff_sign_flag and/or dec_abs_level for a residual coefficient of thetransform block may be parsed, and the residual coefficient may bederived based on the syntax elements. In this case, the syntax elementsmay be sequentially parsed, and a parsing order may be changed. Inaddition, the abs_level_gtx_flag may represent abs_level_gt1_flag,and/or abs_level_gt3_flag. For example, abs_level_gtx_flag[n][0] may bean example of a first transform coefficient level flag(abs_level_gt1_flag), and the abs_level_gtx_flag[n][1] may be an exampleof a second transform coefficient level flag (abs_level_gt3_flag).

Referring to the Table 2 above, last_sig_coeff_x_prefix,last_sig_coeff_y_prefix, last_sig_coeff_x_suffix,last_sig_coeff_y_suffix, sb_coded_flag, sig_coeff_flag,abs_level_gt1_flag, par_level_flag, abs_level_gt3_flag, abs_remainder,coeff_sign_flag, and/or dec_abs_level may be encoded/decoded. Meanwhile,sb_coded_flag may be represented as coded_sub_block_flag.

In an embodiment, the encoding apparatus may encode (x, y) positioninformation of the last non-zero transform coefficient in a transformblock based on the syntax elements last_sig_coeff_x_prefix,last_sig_coeff_y_prefix, last_sig_coeff_x_suffix, andlast_sig_coeff_y_suffix. More specifically, the last_sig_coeff_x_prefixrepresents a prefix of a column position of a last significantcoefficient in a scanning order within the transform block, thelast_sig_coeff_y_prefix represents a prefix of a row position of thelast significant coefficient in the scanning order within the transformblock, the last_sig_coeff_x_suffix represents a suffix of a columnposition of the last significant coefficient in the scanning orderwithin the transform block, and the last_sig_coeff_y_suffix represents asuffix of a row position of the last significant coefficient in thescanning order within the transform block. Here, the significantcoefficient may represent a non-zero coefficient. In addition, thescanning order may be a right diagonal scanning order. Alternatively,the scanning order may be a horizontal scanning order or a verticalscanning order. The scanning order may be determined based on whetherintra/inter prediction is applied to a target block (a CB or a CBincluding a TB) and/or a specific intra/inter prediction mode.

Thereafter, the encoding apparatus may divide the transform block into4×4 sub-blocks, and then indicate whether there is a non-zerocoefficient in the current sub-block using a 1-bit syntax elementcoded_sub_block_flag for each 4×4 sub-block.

If a value of coded_sub_block_flag is 0, there is no more information tobe transmitted, and thus, the encoding apparatus may terminate theencoding process on the current sub-block. Conversely, if the value ofcoded_sub_block_flag is 1, the encoding apparatus may continuouslyperform the encoding process on sig_coeff_flag. Since the sub-blockincluding the last non-zero coefficient does not require encoding forthe coded_sub_block_flag and the sub-block including the DC informationof the transform block has a high probability of including the non-zerocoefficient, coded_sub_block_flag may not be coded and a value thereofmay be assumed as 1.

If the value of coded_sub_block_flag is 1 and thus it is determined thata non-zero coefficient exists in the current sub-block, the encodingapparatus may encode sig_coeff_flag having a binary value according to areverse scanning order. The encoding apparatus may encode the 1-bitsyntax element sig_coeff_flag for each transform coefficient accordingto the scanning order. If the value of the transform coefficient at thecurrent scan position is not 0, the value of sig_coeff_flag may be 1.Here, in the case of a subblock including the last non-zero coefficient,sig_coeff_flag does not need to be encoded for the last non-zerocoefficient, so the coding process for the sub-block may be omitted.Level information coding may be performed only when sig_coeff_flag is 1,and four syntax elements may be used in the level information encodingprocess. More specifically, each sig_coeff_flag[xC][yC] may indicatewhether a level (value) of a corresponding transform coefficient at eachtransform coefficient position (xC, yC) in the current TB is non-zero.In an embodiment, the sig_coeff_flag may correspond to an example of asyntax element of a significant coefficient flag indicating whether aquantized transform coefficient is a non-zero significant coefficient.

A level value remaining after encoding for sig_coeff_flag may be derivedas shown in the following equation. That is, the syntax elementremAbsLevel indicating a level value to be encoded may be derived fromthe following equation.

remAbsLevel=|coeff|−1  [Equation 1]

Herein, coeff means an actual transform coefficient value.

Additionally, abs_level_gt1_flag may indicate whether or notremAbsLevel′ of the corresponding scanning position (n) is greaterthan 1. For example, when the value of abs_level_gt1_flag is 0, theabsolute value of the transform coefficient of the correspondingposition may be 1. In addition, when the value of the abs_level_gt1_flagis 1, the remAbsLevel indicating the level value to be encoded later maybe updated as shown in the following equation.

remAbsLevel=remAbsLevel−1  [Equation 2]

In addition, the least significant coefficient (LSB) value ofremAbsLevel described in Equation 2 described above may be encoded as inEquation 3 below through par_level_flag.

par_level_flag=|coeff|& 1  [Equation 3]

Herein, par_level_flag[n] may indicate a parity of a transformcoefficient level (value) at a scanning position n.

A transform coefficient level value remAbsLevel that is to be encodedafter performing par_level_flag encoding may be updated as shown belowin the following equation.

remAbsLevel=remAbsLevel>>1  [Equation 4]

abs_level_gt3_flag may indicate whether or not remAbsLevel′ of thecorresponding scanning position (n) is greater than 3. Encoding forabs_remainder may be performed only in a case where rem_abs_gt3_flag isequal to 1. A relationship between the actual transform coefficientvalue coeff and each syntax element may be as shown below in thefollowing equation.

|coeff|=sig_coeff_flag+abs_level_gt1_flag+par_level_flag+2*(abs_level_gt3_flag+abs_remainder)  [Equation5]

Additionally, the following table indicates examples related to theabove-described Equation 5.

TABLE 4 |coeff[n]| sig_coeff_flag[n] abs_level_gtX_flag[n][0]par_level_flag[n] abs_level_gtX_flag[n][1] abs_remainder[n] 0 0 1 1 0 21 1 0 0 3 1 1 1 0 4 1 1 0 1 0 5 1 1 1 1 0 6 1 1 0 1 1 7 1 1 1 1 1 8 1 10 1 2 9 1 1 1 1 2 10 1 1 0 1 3 11 1 1 1 1 3 . . . . . . . . . . . .

Herein, coeff indicates a transform coefficient level (value) and mayalso be indicates as an AbsLevel for a transform coefficient.Additionally, a sign of each coefficient may be encoded by usingcoeff_sign_flag, which is a 1-bit symbol.

Also, if the value of the transform skip flag is 1, as shown in Table 3,syntax elements sb_coded_flag, sig_coeff_flag, coeff_sign_flag,abs_level_gtx_flag, par_level_flag and/or abs_remainder for a residualcoefficient of the transform block may be parsed, and the residualcoefficient may be derived based on the syntax elements. In this case,the syntax elements may be sequentially parsed, and a parsing order maybe changed. In addition, the abs_level_gtx_flag may representabs_level_gt1_flag, abs_level_gt3_flag, abs_level_gt5_flag,abs_level_gt7_flag, and/or abs_level_gt9_flag. For example,abs_level_gtx_flag[n][j] may be a flag indicating whether an absolutevalue or a level (a value) of a transform coefficient at a scanningposition n is greater than (j<<1)+1. The condition (j<<1)+1 may beoptionally replaced with a specific threshold such as a first threshold,a second threshold, or the like.

Meanwhile, CABAC provides high performance, but disadvantageously haspoor throughput performance. This is caused by a regular coding engineof the CABAC. Regular encoding (i.e., coding through the regular codingengine of the CABAC) shows high data dependence since it uses aprobability state and range updated through coding of a previous bin,and it may take a lot of time to read a probability interval anddetermine a current state. The throughput problem of the CABAC may besolved by limiting the number of context-coded bins. For example, asshown in Table 2 described above, a sum of bins used to expresssig_coeff_flag, abs_level_gt1_flag, par_level_flag, andabs_level_gt3_flag may be limited to the number of bins depending on asize of a corresponding block. Also, for example, as shown in Table 3described above, a sum of bins used to express sig_coeff_flag,coeff_sign_flag, abs_level_gt1_flag, par_level_flag, abs_level_gt3_flagabs_level_gt5_flag, abs_level_gt7_flag, abs_level_gt9_flag may belimited to the number of bins depending on a size of a correspondingblock. For example, if the corresponding block is a block of a 4×4 size,the sum of bins for the sig_coeff_flag, abs_level_gt1_flag,par_level_flag, abs_level_gt3_flag or sig_coeff_flag, coeff_sign_flag,abs_level_gt1_flag, par_level_flag, abs_level_gt3_flagabs_level_gt5_flag, abs_level_gt7_flag, abs_level_gt9_flag may belimited to 32 (or ex. 28), and if the corresponding block is a block ofa 2×2 size, the sum of bins for the sig_coeff_flag, abs_level_gt1_flag,par_level_flag, abs_level_gt3_flag may be limited to 8 (or ex. 7). Thelimited number of bins may be represented by remBinsPass1 or RemCcbs.Or, for example, for higher CABAC throughput, the number of contextcoded bins may be limited for a block (CB or TB) including a codingtarget CG. In other words, the number of context coded bins may belimited in units of blocks (CB or TB). For example, when the size of thecurrent block is 16×16, the number of context coded bins for the currentblock may be limited to 1.75 times the number of pixels of the currentblock, i.e., 448, regardless of the current CG.

In this case, if all context-coded bins of which the number is limitedare used when a context element is coded, the encoding apparatus maybinarize the remaining coefficients through a method of binarizing thecoefficient as described below, instead of using the context coding, andmay perform bypass encoding. In other words, for example, if the numberof context-coded bins which are coded for 4×4 CG is 32 (or ex. 28), orif the number of context-coded bins which are coded for 2×2 CG is 8 (orex. 7), sig_coeff_flag, abs_level_gt1_flag, par_level_flag,abs_level_gt3_flag which are coded with the context-coded bin may nolonger be coded, and may be coded directly to dec_abs_level. Or, forexample, when the number of context coded bins coded for a 4×4 block is1.75 times the number of pixels of the entire block, that is, whenlimited to 28, the sig_coeff_flag, abs_level_gt1_flag, par_level_flag,and abs_level_gt3_flag coded as context coded bins may not be coded anymore, and may be directly coded as dec_abs_level as shown in Table 5below.

TABLE 5 |coeff[n]| dec_abs_level[n] 0 0 1 1 2 2 3 3 4 4 5 5 6 6 7 7 8 89 9 10 10 11 11 . . . . . .

A value |coeff| may be derived based on dec_abs_level. In this case, atransform coefficient value, i.e., |coeff|, may be derived as shown inthe following equation.

|coeff|=dec_abs_level  [Equation 6]

In addition, the coeff_sign_flag may indicate a sign of a transformcoefficient level at a corresponding scanning position n. That is, thecoeff_sign_flag may indicate the sign of the transform coefficient atthe corresponding scanning position n.

FIG. 11 shows an example of transform coefficients in a 4×4 block.

The 4×4 block of FIG. 11 represents an example of quantizedcoefficients. The block of FIG. 11 may be a 4×4 transform block, or a4×4 sub-block of an 8×8, 16×16, 32×32, or 64×64 transform block. The 4×4block of FIG. 11 may represent a luma block or a chroma block.

Meanwhile, as described above, when an input signal is not a binaryvalue but a syntax element, the encoding apparatus may transform theinput signal into a binary value by binarizing a value of the inputsignal. In addition, the decoding apparatus may decode the syntaxelement to derive a binarized value (e.g., a binarized bin) of thesyntax element, and may de-binarize the binarized value to derive avalue of the syntax element. The binarization process may be performedas a truncated rice (TR) binarization process, a k-th order Exp-Golomb(EGk) binarization process, a limited k-th order Exp-Golomb (limitedEGk), a fixed-length (FL) binarization process, or the like. Inaddition, the de-binarization process may represent a process performedbased on the TR binarization process, the EGk binarization process, orthe FL binarization process to derive the value of the syntax element.

For example, the TR binarization process may be performed as follows.

An input of the TR binarization process may be cMax and cRiceParam for asyntax element and a request for TR binarization. In addition, an outputof the TR binarization process may be TR binarization for symbolValwhich is a value corresponding to a bin string.

Specifically, for example, in the presence of a suffix bin string for asyntax element, a TR bin string for the syntax element may beconcatenation of a prefix bin string and the suffix bin string, and inthe absence of the suffix bin string, the TR bin string for the syntaxelement may be the prefix bin string. For example, the prefix bin stringmay be derived as described below.

A prefix value of the symbolVal for the syntax element may be derived asshown in the following equation.

prefixVal=symbolVal>>cRiceParam  [Equation 7]

Herein, prefixVal may denote a prefix value of the symbolVal. A prefix(i.e., a prefix bin string) of the TR bin string of the syntax elementmay be derived as described below.

For example, if the prefixVal is less than cMax>>cRiceParam, the prefixbin string may be a bit string of length prefixVal+1, indexed by binIdx.That is, if the prefixVal is less than cMax>>cRiceParam, the prefix binstring may be a bit string of which the number of bits is prefixVal+1,indicated by binIdx. A bin for binIdx less than prefixVal may be equalto 1. In addition, a bin for the same binIdx as the prefixVal may beequal to 0.

For example, a bin string derived through unary binarization for theprefixVal may be as shown in the following table.

TABLE 6 prefixVal Bin string 0 0 1 1 0 2 1 1 0 3 1 1 1 0 4 1 1 1 1 0 5 11 1 1 1 0 . . . binIdx 0 1 2 3 4 5

Meanwhile, if the prefixVal is not less than cMax>>cRiceParam, theprefix bin string may be a bit string in which a length iscMax>>cRiceParam and all bits are 1.

In addition, if cMax is greater than symbolVal and if cRiceParam isgreater than 0, a bin suffix bin string of a TR bin string may bepresent. For example, the suffix bin string may be derived as describedbelow.

A suffix value of the symbolVal for the syntax element may be derived asshown in the following equation.

suffixVal=symbolVal−((prefixVal)<<cRiceParam)  [Equation 8]

Herein, suffixVal may denote a suffix value of the symbolVal.

A suffix of a TR bin string (i.e., a suffix bin string) may be derivedbased on an FL binarization process for suffixVal of which a value cMaxis (1<<cRiceParam)−1.

Meanwhile, if a value of an input parameter, i.e., cRiceParam, is 0, theTR binarization may be precisely truncated unary binarization, and mayalways use the same value cMax as a possible maximum value of a syntaxelement to be decoded.

In addition, for example, the EGk binarization process may be performedas follows. A syntax element coded with ue(v) may be a syntax elementsubjected to Exp-Golomb coding.

For example, a 0-th order Exp-Golomb (EGO) binarization process may beperformed as follows.

A parsing process for the syntax element may begin with reading a bitincluding a first non-zero bit starting at a current position of abitstream and counting the number of leading bits equal to 0. Theprocess may be represented as shown in the following table.

TABLE 7   leadingZeroBits = −1 for( b = 0; !b; leadingZeroBits++ )   b =read_bits( 1 )

In addition, a variable ‘codeNum’ may be derived as shown in thefollowing equation.

codeNum=2^(leadingZeroBits)−1+read_bits(leadingZeroBits)  [Equation 9]

Herein, a value returned from read_bits(leadingZeroBits), that is, avalue indicated by read_bits(leadingZeroBits), may be interpreted asbinary representation of an unsigned integer for a most significant bitrecorded first.

A structure of an Exp-Golomb code in which a bit string is divided intoa “prefix” bit and a “suffix” bit may be represented as shown in thefollowing table.

TABLE 8 Bit string form Range of codeNum 1 0 0 1 x₀ 1 . . . 2 0 0 1 x₁x₀ 3 . . . 6 0 0 0 1 x₂ x₁ x₀  7 . . . 14 0 0 0 0 1 x₃ x₂ x₁ x₀ 15 . . .30 0 0 0 0 0 1 x₄ x₃ x₂ x₁ x₀ 31 . . . 62 . . . . . .

The “prefix” bit may be a bit parsed as described above to calculateleadingZeroBits, and may be represented by 0 or 1 of a bit string inTable 8. That is, the bit string disclosed by 0 or 1 in Table 8 abovemay represent a prefix bit string. The “suffix” bit may be a bit parsedin the computation of codeNum, and may be represented by xi in Table 8above. That is, a bit string disclosed as xi in Table 8 above mayrepresent a suffix bit string. Herein, i may be a value in the range ofLeadingZeroBits−1. In addition, each xi may be equal to 0 or 1.

A bit string assigned to the codeNum may be as shown in the followingtable.

TABLE 9 Bit string codeNum 1 0 0 1 0 1 0 1 1 2 0 0 1 0 0 3 0 0 1 0 1 4 00 1 1 0 5 0 0 1 1 1 6 0 0 0 1 0 0 0 7 0 0 0 1 0 0 1 8 0 0 0 1 0 1 0 9 .. . . . .

If a descriptor of the syntax element is ue(v), that is, if the syntaxelement is coded with ue(v), a value of the syntax element may be equalto codeNum.

In addition, for example, the EGk binarization process may be performedas follows.

An input of the EGk binarization process may be a request for EGkbinarization. In addition, the output of the EGk binarization processmay be EGk binarization for symbolVal, i.e., a value corresponding to abin string.

A bit string of the EGk binarization process for symbolVal may bederived as follows.

TABLE 10   absV = Abs( symbol Val ) stopLoop = 0 do   if( absV >= ( 1 <<k ) ) {     put( 1 )     absV = absV − ( 1 << k )     k++   } else {    put( 0 )     while( k−− )       put( ( absV >> k ) & 1 )    stopLoop = 1   } while( !stopLoop )

Referring to Table 10 above, a binary value X may be added to an end ofa bin string through each call of put(X). Herein, X may be 0 or 1.

In addition, for example, the limited EGk binarization process may beperformed as follows.

An input of the limited EGk binarization process may be a request forlimited EGk binarization, a rice parameter riceParam, log2TransformRangeas a variable representing a binary logarithm of a maximum value, andmaxPreExtLen as a variable representing a maximum prefix extensionlength. In addition, an output of the limited EGk binarization processmay be limited EGk binarization for symbolVal as a value correspondingto an empty string.

A bit string of the limited EGk binarization process for the symbolValmay be derived as follows.

TABLE 11    codeValue = symbolVal >> riceParam PrefixExtensionLength = 0while( ( PrefixExtensionLength < maxPrefixExtensionLength ) &&     (code Value > ( ( 2 << PrefixExtensionLength ) − 2 ) ) ) {  PrefixExtensionLength++   put( 1 ) } if( PrefixExtensionLength = =maxPrefixExtensionLength )   escapeLength = log2TransformRange else {  escapeLength = PrefixExtensionLength + riceParam   put( 0 ) }symbolVal = symbolVal − ( ( ( 1 << PrefixExtensionLength ) − 1 ) <<riceParam ) while( ( escapeLength−− ) > 0 )   put( ( symbolVal >>escapeLength ) & 1 )

In addition, for example, the FL binarization process may be performedas follows.

An input of the FL binarization process may be a request for FLbinarization and cMax for the syntax element. In addition, an output ofthe FL binarization process may be FL binarization for symbolVal as avalue corresponding to a bin string.

FL binarization may be configured by using a bit string of which thenumber of bits has a fixed length of symbolVal. Herein, the fixed-lengthbit may be an unsigned integer bit string. That is, a bit string forsymbolVal as a symbol value may be derived through FL binarization, anda bit length (i.e., the number of bits) of the bit string may be a fixedlength.

For example, the fixed length may be derived as shown in the followingequation.

fixedLength=Ceil(Log 2(cMax+1))  [Equation 10]

Indexing of bins for FL binarization may be a method using a value whichincreases orderly from a most significant bit to a least significantbit. For example, a bin index related to the most significant bit may bebinIdx=0.

Meanwhile, for example, a binarization process for a syntax elementabs_remainder in the residual information may be performed as follows.

An input of the binarization process for the abs_remainder may be arequest for binarization of a syntax element abs_remainder[n], a colourcomponent cIdx, and a luma position (x0, y0). The luma position (x0, y0)may indicate a top-left sample of a current luma transform block basedon the top-left luma sample of a picture.

An output of the binarization process for the abs_remainder may bebinarization of the abs_remainder (i.e., a binarized bin string of theabs_remainder). Available bin strings for the abs_remainder may bederived through the binarization process.

A rice parameter cRiceParam for the abs_remainder[n] may be derivedthrough a rice parameter derivation process performed by inputting thecolor component cIdx and luma position (x0, y0), the current coefficientscan position (xC, yC), log2TbWidth, which is the binary logarithm ofthe width of the transform block, and log2TbHeight, which is the binarylogarithm of the height of the transform block. A detailed descriptionof the rice parameter derivation process will be described later.

In addition, for example, cMax for abs_remainder[n] to be currentlycoded may be derived based on the rice parameter cRiceParam. The cMaxmay be derived as shown in the following equation.

cMax=6<<cRiceParam  [Equation 11]

Meanwhile, binarization for the abs_remainder, that is, a bin string forthe abs_remainder, may be concatenation of a prefix bin string and asuffix bin string in the presence of the suffix bin string. In addition,in the absence of the suffix bin string, the bin string for theabs_remainder may be the prefix bin string.

For example, the prefix bin string may be derived as described below.

A prefix value prefixVal of the abs_remainder[n] may be derived as shownin the following equation.

prefixVal=Min(cMax,abs_remainder[n])  [Equation 12]

A prefix of the bin string (i.e., a prefix bin string) of theabs_remainder[n] may be derived through a TR binarization process forthe prefixVal, in which the cMax and the cRiceParam are used as aninput.

If the prefix bin string is identical to a bit string in which all bitsare 1 and a bit length is 6, a suffix bin string of the bin string ofthe abs_remainder[n] may exist, and may be derived as described below.

The rice parameter deriving process for the dec_abs_level[n] may be asfollows.

An input of the rice parameter deriving process may be a colourcomponent index cIdx, a luma position (x0, y0), a current coefficientscan position (xC, yC), log2TbWidth as a binary logarithm of a width ofa transform block, and log2TbHeight as a binary logarithm of a height ofthe transform block. The luma position (x0, y0) may indicate a top-leftsample of a current luma transform block based on a top-left luma sampleof a picture. In addition, an output of the rice parameter derivingprocess may be the rice parameter cRiceParam.

For example, a variable locSumAbs may be derived similarly to a pseudocode disclosed in the following table, based on an array AbsLevel[x][y]for a transform block having the given component index cIdx and thetop-left luma position (x0, y0).

TABLE 12   locSumAbs = 0 if( xC < (1 << log2TbWidth) − 1 ) {  locSumAbs+= AbsLevel[ xC + 1 ][ yC ]  if( xC < ( 1 << log2TbWidth) − 2 )     locSumAbs += AbsLevel[ xC + 2 ][ yC ]           if( yC < (1 <<log2TbHeight) − 1 )      locSumAbs += AbsLevel[ xC + 1 ][ yC + 1 ](1532) } if( yC < (1 << log2TbHeight) − 1 ) {  locSumAbs += AbsLevel[ xC][ yC + 1 ]  if( yC <(1 << log2TbHeight) − 2 )      locSumAbs +=AbsLevel[ xC ][ yC + 2 ] } locSumAbs = Clip3( 0, 31, locSumAbs −baseLevel * 5 )

Then, based on the given variable locSumAbs, the rice parametercRiceParam may be derived as shown in the following table.

TABLE 13 locSumAbs 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 cRiceParam 0 00 0 0 0 0 1 1 1 1 1 1 1 2 2 locSumAbs 16 17 18 19 20 21 22 23 24 25 2627 28 29 30 31 cRiceParam 2 2 2 2 2 2 2 2 2 2 2 2 3 3 3 3

Also, for example, in the rice parameter derivation process forabs_remainder[n], the baseLevel may be set to 4.

Alternatively, for example, the rice parameter cRiceParam may bedetermined based on whether a transform skip is applied to a currentblock. That is, if a transform is not applied to a current TB includinga current CG, in other words, if the transform skip is applied to thecurrent TB including the current CG, the rice parameter cRiceParam maybe derived to be 1.

Also, a suffix value suffixVal of the abs_remainder may be derived asshown in the following equation.

suffixVal=abs_remainder[n]cMax  [Equation 13]

A suffix bin string of the bin string of the abs_remainder may bederived through a limited EGk binarization process for the suffixVal inwhich k is set to cRiceParam+1, riceParam is set to cRiceParam, andlog2TransformRange is set to 15, and maxPreExtLen is set to 11.

Meanwhile, for example, a binarization process for a syntax elementdec_abs_level in the residual information may be performed as follows.

An input of the binarization process for the dec_abs_level may be arequest for binarization of a syntax element dec_abs_level[n], a colourcomponent cIdx, a luma position (x0, y0), a current coefficient scanposition (xC, yC), log2TbWidth as a binary logarithm of a width of atransform block, and log2TbHeight as a binary logarithm of a height ofthe transform block. The luma position (x0, y0) may indicate a top-leftsample of a current luma transform block based on a top-left luma sampleof a picture.

An output of the binarization process for the dec_abs_level may bebinarization of the dec_abs_level (i.e., a binarized bin string of thedec_abs_level). Available bin strings for the dec_abs_level may bederived through the binarization process.

A rice parameter cRiceParam for dec_abs_level[n] may be derived througha rice parameter deriving process performed with an input of the colourcomponent cIdx, the luma position (x0, y0), the current coefficient scanposition (xC, yC), the log2TbWidth as the binary logarithm of the widthof the transform block, and the log2TbHeight as the binary logarithm ofthe height of the transform block. The rice parameter deriving processwill be described below in detail.

In addition, for example, cMax for the dec_abs_level[n] may be derivedbased on the rice parameter cRiceParam. The cMax may be derived as shownin the following table.

cMax=6<<cRiceParam  [Equation 14]

Meanwhile, binarization for the dec_abs_level[n], that is, a bin stringfor the dec_abs_level[n], may be concatenation of a prefix bin stringand a suffix bin string in the presence of the suffix bin string. Inaddition, in the absence of the suffix bin string, the bin string forthe dec_abs_level[n] may be the prefix bin string.

For example, the prefix bin string may be derived as described below.

A prefix value prefixVal of the dec_abs_level[n] may be derived as shownin the following equation.

prefixVal=Min(cMax,dec_abs_level[n])  [Equation 15]

A prefix of the bin string (i.e., a prefix bin string) of thedec_abs_level[n] may be derived through a TR binarization process forthe prefixVal, in which the cMax and the cRiceParam are used as aninput.

If the prefix bin string is identical to a bit string in which all bitsare 1 and a bit length is 6, a suffix bin string of the bin string ofthe dec_abs_level[n] may exist, and may be derived as described below.

The rice parameter deriving process for the dec_abs_level[n] may be asfollows.

An input of the rice parameter deriving process may be a colourcomponent index cIdx, a luma position (x0, y0), a current coefficientscan position (xC, yC), log2TbWidth as a binary logarithm of a width ofa transform block, and log2TbHeight as a binary logarithm of a height ofthe transform block. The luma position (x0, y0) may indicate a top-leftsample of a current luma transform block based on a top-left luma sampleof a picture. In addition, an output of the rice parameter derivingprocess may be the rice parameter cRiceParam.

For example, a variable locSumAbs may be derived similarly to a pseudocode disclosed in the following table, based on an array AbsLevel[x][y]for a transform block having the given component index cIdx and thetop-left luma position (x0, y0).

TABLE 14   locSumAbs = 0 if( xC < (1 << log2TbWidth) − 1 ) {  locSumAbs+= AbsLevel[ xC + 1 ][ yC ]  if( xC < (1 << log2TbWidth) − 2 )     locSumAbs += AbsLevel[ xC + 2 ][ yC ]  if( yC < (1 << log2TbHeight)− 1 )      locSumAbs += AbsLevel[ xC + 1 ][ yC + 1 ] (1532) } if( yC <(1 << log2TbHeight) − 1 ) {  locSumAbs += AbsLevel[ xC ][ yC + 1 ]  if(yC < (1 << log2TbHeight) − 2 )      locSumAbs += AbsLevel[ xC ][ yC + 2] } locSumAbs = Clip3( 0, 31, locSumAbs − baseLevel * 5 )

Then, based on the given variable locSumAbs, the rice parametercRiceParam may be derived as shown in the following table.

TABLE 15 locSumAbs 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 cRiceParam 0 00 0 0 0 0 1 1 1 1 1 1 1 2 2 locSumAbs 16 17 18 19 20 21 22 23 24 25 2627 28 29 30 31 cRiceParam 2 2 2 2 2 2 2 2 2 2 2 2 3 3 3 3

Also, for example, in the rice parameter derivation process fordec_abs_level[n], the baseLevel may be set to 0, and the ZeroPos[n] maybe derived as follows.

ZeroPos[n]=(QState<2?1:2)<<cRiceParam  [Equation 16]

In addition, a suffix value suffixVal of the dec_abs_level[n] may bederived as shown in the following equation.

suffixVal=dec_abs_level[n]−cMax  [Equation 17]

A suffix bin string of the bin string of the dec_abs_level[n] may bederived through a limited EGk binarization process for the suffixVal inwhich k is set to cRiceParam+1, truncSuffixLen is set to 15, andmaxPreExtLen is set to 11.

Meanwhile, the RRC and the TSRC may have the following differences.

-   -   For example, the Rice parameter for the syntax element        abs_remainder[ ] in TSRC may be derived as 1. The Rice parameter        cRiceParam of the syntax element abs_remainder[ ] in RRC may be        derived based on the lastAbsRemainder and the lastRiceParam as        described above, but the Rice parameter cRiceParam of the syntax        element abs_remainder[ ] in TSRC may be derived as 1. That is,        for example, when transform skip is applied to the current block        (e.g., the current TB), the Rice parameter cRiceParam for        abs_remainder[ ] of the TSRC for the current block may be        derived as 1.    -   Also, for example, referring to Table 3 and Table 4, in the RRC,        abs_level_gtx_flag[n][0] and/or abs_level_gtx_flag[n][1] may be        signaled, but in the TSRC, abs_level_gtx_flag[n][0],        abs_level_gtx_flag[n][1], abs_level_gtx_flag[n][2],        abs_level_gtx_flag[n][3], and abs_level_gtx_flag[n][4] may be        signaled. Here, the abs_level_gtx_flag[n][0] may be expressed as        abs_level_gt1_flag or a first coefficient level flag, the        abs_level_gtx_flag[n][1] may be expressed as abs_level_gt3_flag        or a second coefficient level flag, the abs_level_gtx_flag[n][2]        may be expressed as abs_level_gt5_flag or a third coefficient        level flag, the abs_level_gtx_flag[n][3] may be expressed as        abs_level_gt7_flag or a fourth coefficient level flag, and the        abs_level_gtx_flag[n] [4] may be expressed as abs_level_gt9_flag        or a fifth coefficient level flag. Specifically, the first        coefficient level flag may be a flag for whether a coefficient        level is greater than a first threshold (for example, 1), the        second coefficient level flag may be a flag for whether a        coefficient level is greater than a second threshold (for        example, 3), the third coefficient level flag may be a flag for        whether a coefficient level is greater than a third threshold        (for example, 5), the fourth coefficient level flag may be a        flag for whether a coefficient level is greater than a fourth        threshold (for example, 7), the fifth coefficient level flag may        be a flag for whether a coefficient level is greater than a        fifth threshold (for example, 9). As described above, in the        TSRC, compared to the RRC, abs_level_gtx_flag[n][0],        abs_level_gtx_flag[n][1], and abs_level_gtx_flag[n][2],        abs_level_gtx_flag[n][3], abs_level_gtx_flag[n][4] may be        further included.    -   Also, for example, in the RRC, the syntax element        coeff_sign_flag may be bypass coded, but in the TSRC, the syntax        element coeff_sign_flag may be bypass coded or context coded.    -   Also, for example, when the context-coded bin for the current        block is exhausted, in the RRC, it may be coded as the syntax        element dec_abs_level, but in the TSRC, it may be coded as a        syntax element abs_remainder.    -   Also, for example, the order of parsing transform coefficients        of the RRC may be parsed in a promised order in the bottom        right-top left direction based on the last non-zero coefficient,        but in the case of the TSRC, it may be parsed in a promised        order in the upper left-bottom right direction, and the position        of the last non-zero coefficient may be omitted.    -   Also, for example, in the RRC, a dependent quantization (DQ) or        a sign data hiding method (SDH) method may be applied, but in        the TSRC, dependent quantization and sign data hiding methods        may not be used.

Also, a sign data hiding (SDH) method may be proposed in relation toresidual coding. The sign data hiding method may be as follows.

In deriving the transform coefficient, the sign of the transformcoefficient may be derived based on a 1-bit sign flag (theabove-described syntax element coeff_sign_flag). In this regard, SDH mayindicate a technique for omitting explicit signaling of coeff_sign_flagfor the first significant transform coefficient in asub-block/coefficient group (CG) in order to improve coding efficiency.Here, the value of coeff_sign_flag for the first significant transformcoefficient may be derived based on the sum of absolute levels (i.e.,absolute values) of the significant transform coefficients in thecorresponding sub-block/coefficient group. That is, the sign of thefirst significant transform coefficient may be derived based on the sumof absolute levels of the significant transform coefficients in thecorresponding sub-block/coefficient group. Meanwhile, the significanttransform coefficient may refer to a non-zero transform coefficientwhose (absolute) value is not 0. For example, when the sum of absolutelevels for the significant transform coefficients is even, the value ofcoeff_sign_flag for the first significant transform coefficient may bederived as 1, while, when the sum of absolute levels for the significanttransform coefficients is odd, the value of coeff_sign_flag for thefirst significant transform coefficient may be derived as 0. In otherwords, for example, when the sum of absolute levels for the significanttransform coefficients is even, the sign for the first significanttransform coefficient may be derived as a negative value, while, whenthe sum of absolute levels for the significant transform coefficients isodd, the sign for the first significant transform coefficient may bederived as a positive value. Alternatively, for example, when the sum ofabsolute levels for the significant transform coefficients is even, thevalue of coeff_sign_flag for the first significant transform coefficientmay be derived as 0, while, when the sum of absolute levels for thesignificant transform coefficients is odd, the value of coeff_sign_flagfor the first significant transform coefficient may be derived as 1. Inother words, for example, when the sum of absolute levels for thesignificant transform coefficients is even, the sign for the firstsignificant transform coefficient may be derived as a positive value,while, when the sum of absolute levels for the significant transformcoefficients is odd, the sign for the first significant transformcoefficient may be derived as a negative value.

For example, the SDH in the residual syntax may be expressed as shown inthe following table.

TABLE 16 } signHiddenFlag = sh_sign_data_hiding_used_flag &&   (lastSigScanPosSb − firstSigScanPosSb > 3 ? 1 : 0 ) for( n = numSbCoeff −1; n >= 0; n− − ) {  xC = ( xS << log2SbW ) + DiagScanOrder[ log2SbW ][ log2SbH ][ n ][ 0 ]  yC = ( yS << log2SbH ) + DiagScanOrder[ log2SbW ][ log2SbH ][ n ][ 1 ]  if( ( AbsLevel[ xC ][ yC ] > 0 ) &&   (!signHiddenFlag | | ( n != firstSigScanPosSb ) ) )   coeff_sign_flag[ n] ae(v)

Referring to Table 16, the variable signHiddenFlag may indicate whetherthe SDH is applied. The variable signHiddenFlag may be also calledsignHidden. For example, when the value of the variable signHiddenFlagis 0, the variable signHiddenFlag may indicate that the SDH is notapplied, while, when the value of the variable signHiddenFlag is 1, thevariable signHiddenFlag may indicate that the SDH is applied. Forexample, the value of the variable signHiddenFlag may be set based onsignaled flag information (e.g., sh_sign_data_hiding_used_flag orpic_sign_data_hiding_enabled_flag or sps_sign_data_hiding_enabled_flag).Also, for example, the value of the variable signHiddenFlag may be setbased on lastSigScanPosSb and firstSigScanPosSb. Here, lastSigScanPosSbmay indicate the position of the last significant transform coefficientsearched in the corresponding sub-block/coefficient group according tothe scan order, and firstSigScanPosSb may indicate a position of a firstsignificant transform coefficient searched in a correspondingsub-block/coefficient group according to a scan order. In general,lastSigScanPosSb may be located in a relatively high frequency componentregion than firstSigScanPosSb. Accordingly, whenlastSigScanPosSb−firstSigScanPosSb is greater than a predeterminedthreshold, the signHidden value may be derived as 1 (that is, SDH isapplied), while otherwise the signHidden value may be derived as 0 (thatis, SDH is not applied). Here, for example, referring to Table 35, thethreshold value may be set to 3.

In addition, referring to Table 16, even if the value of signHiddenFlagis 0 (i.e., !signHiddenFlag), if the current coefficient is not thefirst significant coefficient in the (sub)block according to the scanorder (i.e., n !=firstSigScanPosSb), then the coeff_sign_flag[n] for thecurrent coefficient may be explicitly signaled.

Also, referring to Table 16, if the value of signHiddenFlag is 1, andthe current coefficient is the first significant coefficient in the(sub)block according to the scan order (i.e., n=first SigScanPosSb),then explicit signaling of coeff_sign_flag[n] for the currentcoefficient may be omitted. In this case, the value ofcoeff_sign_flag[n] for the current coefficient (i.e., the firstsignificant coefficient) may be derived as follows. For example, thevalue of coeff_sign_flag[n] for the first significant coefficient may bederived based on coeff_sign_flag[n] values for the significantcoefficients in the corresponding (sub) block. For example, when the sumof coeff_sign_flag[n] values for the significant coefficients is even,coeff_sign_flag[n] for the first significant coefficient may be derivedas 1, while, when the sum of coeff_sign_flag[n] values for the remainingsignificant coefficients is odd, coeff_sign_flag[n] for the firstsignificant coefficient may be derived as 0. Alternatively, when the sumof coeff_sign_flag[n] values for the significant coefficients is even,coeff_sign_flag[n] for the first significant coefficient may be derivedas 0, while, when the sum of coeff_sign_flag[n] values for thesignificant coefficients is odd, coeff_sign_flag[n] for the firstsignificant coefficient may be derived as 1.

Meanwhile, if in high-level syntax (VPS, SPS, PPS, slice header syntax,etc.) or low-level syntax (slice data syntax, coding unit syntax,transformation unit syntax, etc.), the above-described sign data hidingis activated, and if the sh_ts_residual_coding_disabled_flag is 1, thenthe sign data hiding process of RRC may be used in lossless coding.Accordingly, the lossless coding may become impossible due to incorrectsettings in the encoding apparatus. Alternatively, if loss coding (thatis, an irreversible coding method) other than lossless coding isapplied, and the residual signal to which the transform skip has beenapplied is coded with RRC while at the same time BDPCM is applied, thenthe BDPCM may be subjected to coding loss because SDH is performed inaccordance with the SDH application condition, despite the fact that theinterval in which the residual value becomes 0 occurs more frequentlythan in the general case due to the difference between the residuals.Specifically, for example, if significant transform coefficients(non-zero residual data) exist at positions 0 and 15 in the CG,respectively, and the values of the transform coefficients at theremaining positions in the CG are 0, then SDH may be applied to the CGaccording to the above-described SDH application conditions, and thussign data (i.e., coding of a sign flag) for the first significanttransform coefficient of the CG may be omitted. Accordingly, in thiscase, the parity of only two residual data of the CG may be adjusted inthe quantization step in order to omit the sign data, and thus morecoding loss may occur than in the case where SDH is not applied. Suchcases may also occur in blocks to which the BDPCM is not applied, butdue to the characteristics of BDPCM, the level is lowered through thedifference with the neighboring residual, so disadvantageous cases mayoccur more frequently in applying the SDH.

Accordingly, in this document, in order to prevent an unintended codingloss or malfunction caused by using together SDH and residual codingwhen sh_ts_residual_coding_disabled_flag=1 (that is, coding the residualsamples of transform skip blocks in the current slice with the RRC),there are provided embodiments for setting a dependency/constraintbetween the two techniques described above.

Meanwhile, as described above, the residual data coding method mayinclude regular residual coding (RRC) and transform skip residual coding(TSRC).

As shown in Table 1, the residual data coding method for the currentblock among the above two methods may be determined based on values oftransform_skip_flag and sh_ts_residual_coding_disabled_flag. Here, thesyntax element sh_ts_residual_coding_disabled_flag may indicate whetherthe TSRC is enabled. Accordingly, even when the transform_skip_flagindicates that transform is skipped, ifsh_ts_residual_coding_disabled_flag indicates that the TSRC is notenabled, then syntax elements according to RRC with respect to thetransform skip block may be signaled. That is, when the value oftransform_skip_flag is 0 or the value ofsh_ts_residual_coding_disabled_flag is 1, the RRC may be used, whileotherwise the TSRC may be used.

This document proposes as an embodiment a method in whichsh_ts_residual_coding_disabled_flag is dependent onpic_sign_data_hiding_enabled_flag. For example, the syntax elementsproposed in this embodiment may be as shown in the following table.

TABLE 17 Descriptor slice header( ) {   picture header in slice headerflag u(1)   if( picture header in slice header flag )    picture headerstructure( )  (...)  if(!pic sign data hiding enabled flag)    sh tsresidual coding disabled flag u(1)   if( ph lmcs enabled flag )    slicelmcs enabled flag u(1)   if( pic scaling list enabled flag )    slicescaling list present flag u(1)   if( NumEntryPoints > 0 ) {    offsetlen minus1 ue(v)    for( i = 0; i < NumEntryPoints; i++ )    entry_point_offset_minus1[ i ] u(v)   }   if( slice header extensionpresent flag ) {    slice_header_extension_length ue(v)    for( i = 0; i< slice header extension length; i++)    slice_header_extension_data_byte[ i ] u(8)   }   byte alignment( ) }

Here, for example, the pic_sign_data_hiding_enabled_flag may be a flagfor whether the sign data hiding is enabled. For example,pic_sign_data_hiding_enabled_flag may indicate whether sign data hidingis enabled. That is, for example, pic_sign_data_hiding_enabled_flag mayindicate whether sign data hiding is enabled for blocks of pictures fora sequence or picture header structure (i.e., picture_header_structure()). For example, pic_sign_data_hiding_enabled_flag may indicate whethera sign data hiding used flag indicating whether sign data hiding is usedfor the current slice may be present. For example, thepic_sign_data_hiding_enabled_flag whose value is 1 may indicate that thesign data hiding is enabled, while the pic_sign_data_hiding_enabled_flagwhose value is 0 may indicate that the sign data hiding is not enabled.For example, the pic_sign_data_hiding_enabled_flag whose value is 1 mayindicate that the sign data hiding used flag may be present, while thepic_sign_data_hiding_enabled_flag whose value is 0 may indicate that thesign data hiding used flag is not present.

According to Table 17 described above,sh_ts_residual_coding_disabled_flag may be signaled only when sign datahiding is not enabled. Additionally, when sign data hiding is enabled,sh_ts_residual_coding_disabled_flag may not be signaled, and the valueof sh_ts_residual_coding_disabled_flag may be inferred to be 0 (codingthe residual samples of the transform skip block in the current slicewith TSRC syntax) or 1 (coding the residual samples of the transformskip block in the current slice with RRC syntax).

Here, for example, the pic_sign_data_hiding_enabled_flag may be signaledas a picture header syntax or a slice header syntax. For example, whenthe pic_sign_data_hiding_enabled_flag is signaled as a syntax other thanthe picture header syntax, it may be called another name. For example,the pic_sign_data_hiding_enabled_flag may be represented assh_sign_data_hiding_enabled_flag when signaled in a slice header.Additionally, sh_ts_residual_coding_disabled_flag may be signaled as aslice header syntax, or may be signaled in a high level syntax(HLS)(e.g., SPS syntax/VPS syntax/DPS syntax, etc.) or low level (CU/TU)other than the slice header syntax. When the residual coding method isdetermined by whether SDH is enabled regardless of an upper/lowerrelationship of signaled syntaxes or a position on the syntax, it may beinterpreted as conforming to the present embodiment.

Meanwhile, according to the conventional image/video coding, inhigh-level syntax (SPS syntax/VPS syntax/DPS syntax/picture headersyntax/slice header syntax, etc.) or low level (CU/TU), the SDH isenabled, and when sh_ts_residual_coding_disabled_flag is 1, the SDH inthe above-described RRC may be used for lossless coding, so the losslesscoding may become impossible due to an incorrect setting in the encodingapparatus. Accordingly, in this document, in order to prevent anunintended coding loss or malfunction caused by using together SDH andresidual coding when sh_ts_residual_coding_disabled_flag=1 (that is,coding the residual samples of transform skip blocks in the currentslice with the RRC), there is provided an embodiment in which the SDH isnot used in coding the level of the transform coefficient when the valueof transform_skip_flag is 1. The residual coding syntax according to theproposed embodiment may be as in the following table.

TABLE 18 Descriptor residual coding( x0, y0, log2TbWidth, log2TbHeight,cIdx ) {  if( sps_mts_enabled_flag && cu_sbt_flag && cIdx = = 0 &&   log2TbWidth = = 5 && log2TbHeight < 6 )   log2ZoTbWidth = 4  else  log2ZoTbWidth = Min( log2TbWidth, 5 )  if( sps_mts_enabled_flag &&cu_sbt_flag && cIdx = = 0 &&    log2TbWidth < 6 && log2TbHeight = = 5 )  log2ZoTbHeight = 4  else   log2ZoTbHeight = Min( log2TbHeight, 5 ) if( log2TbWidth > 0 )   last_sig_coeff_x_prefix ae(v)  if(log2TbHeight > 0 )   last_sig_coeff_y_prefix ae(v)  if( last sig coeff xprefix > 3 )   last sig coeff x suffix ae(v)  if( last sig coeff yprefix > 3 )   last sig coeff y suffix ae(v)  log2TbWidth =log2ZoTbWidth  log2TbHeight = log2ZoTbHeight  remBinsPass1 = ( ( 1 << (log2TbWidth + log2TbHeight ) ) * 7 ) >> 2  log2SbW = ( Min( log2TbWidth,log2TbHeight ) < 2 ? 1 : 2 )  log2SbH = log2SbW  if( log2TbWidth +log2TbHeight > 3 )   if( log2TbWidth < 2 ) {    log2SbW = log2TbWidth   log2SbH = 4 − log2SbW   } else if( log2TbHeight < 2 ) {    log2SbH =log2TbHeight    log2SbW = 4 − log2SbH   }  numSbCoeff = 1 << ( log2SbW +log2SbH )  lastScanPos = numSbCoeff  lastSubBlock = ( 1 << (log2TbWidth + log2TbHeight − ( log2SbW + log2Sb H ) ) ) − 1  do {   if(lastScanPos = = 0 ) {    lastScanPos = numSbCoeff    lastSubBlock− −   }  lastScanPos− −   xS = DiagScanOrder[ log2TbWidth − log2SbW ][log2TbHeight − log2SbH ]         [ lastSubBlock ][ 0 ]   yS =DiagScanOrder[ log2TbWidth − log2SbW ][ log2TbHeight − log2SbH ]        [ lastSubBlock ][ 1 ]   xC = ( xS << log2SbW ) + DiagScanOrder[log2SbW ][ log2SbH ][ lastScan Pos ][ 0 ]   yC = ( yS << log2SbH ) +DiagScanOrder[ log2SbW ][ log2SbH ][ lastScan Pos ][ 1 ]  } while( ( xC!= LastSignificantCoeffX ) | | ( yC != LastSignificantCoeffY ) )  if(lastSubBlock = = 0 && log2TbWidth >= 2 && log2TbHeight >= 2 & &   !transform skip flag[ x0 ][ y0 ][ cIdx ] && lastScanPos > 0 )  LfnstDcOnly = 0  if( ( lastSubBlock > 0 && log2TbWidth >= 2 &&log2TbHeight >= 2 ) | |    ( lastScanPos > 7 && ( log2TbWidth = = 2 | |log2TbWidth = = 3 ) & &    log2TbWidth = = log2TbHeight ) )  LfnstZeroOutSigCoeffFlag = 0  if( ( lastSubBlock > 0 | | lastScanPos >0 ) && cIdx = = 0 )   MtsDcOnly = 0  QState = 0  for( i = lastSubBlock;i >= 0; i− − ) {   startQStateSb = QState   xS = DiagScanOrder[log2TbWidth − log2SbW ][ log2TbHeight − log2SbH ]         [ i ][ 0 ]  yS = DiagScanOrder[ log2TbWidth − log2SbW ][ log2TbHeight − log2SbH ]        [ i ][ 1 ]   inferSbDcSigCoeffFlag = 0   if( i < lastSubBlock &&i > 0 ) {    coded_sub_block_flag[ xS ][ yS ] ae(v)   inferSbDcSigCoeffFlag = 1   }   if( coded_sub_block_flag[ xS ][ yS ]&& ( xS > 3 | | yS > 3 ) && cIdx = = 0 )    MtsZeroOutSigCoeffFlag = 0  firstSigScanPosSb = numSbCoeff   lastSigScanPosSb = −1   firstPosMode0= ( i = = lastSubBlock ? lastScanPos : numSbCoeff − 1 )   firstPosMode1= firstPosMode0   for( n = firstPosMode0; n >= 0 && remBinsPass1 >= 4;n− − ) {    xC = ( xS << log2SbW ) + DiagScanOrder[ log2SbW ][ log2SbH][ n ] [ 0 ]    yC = ( yS << log2SbH ) + DiagScanOrder[ log2SbW ][log2SbH ][ n ] [ 1 ]    if( coded_sub_block_flag[ xS ][ yS ] && ( n > 0| | !inferSbDcSigCoeffF lag ) &&     ( xC != LastSignificantCoeffX | |yC != Last SignificantCoeffY ) ) {     sig_coeff_flag[ xC ][ yC ] ae(v)    remBinsPass1− −     if( sig coeff flag[ xC ][ yC ] )     inferSbDcSigCoeffFlag = 0    }    if( sig coeff flag[ xC ][ yC ] ){     abs_level_gtx_flag[ n ][ 0 ] ae(v)     remBinsPass1− −     if( abslevel gtx flag[ n ][ 0 ] ) {      par_level_flag[ n ] ae(v)     remBinsPass1− −      abs_level_gtx_flag[ n ][ 1 ] ae(v)     remBinsPass1− −     }     if( lastSigScanPosSb = = −1 )     lastSigScanPosSb = n     firstSigScanPosSb = n    }   AbsLevelPass1[ xC ][ yC ] = sig_coeff_flag[ xC ][ yC ] +par_level_flag [ n ] +           abs_level_gtx_flag[ n ][ 0 ] + 2 *abs_level_gtx_flag[ n ] [ 1 ]    if( ph dep quant enabled flag )    QState = QStateTransTable[ QState ][ AbsLevelPass1[ xC ][ yC ] & 1 ]   firstPosMode1 = n − 1   }   for( n = firstPosMode0; n >firstPosMode1; n− − ) {    xC = ( xS << log2SbW ) + DiagScanOrder[log2SbW ][ log2SbH ][ n ] [ 0 ]    yC = ( yS << log2SbH ) +DiagScanOrder[ log2SbW ][ log2SbH ][ n ] [ 1 ]    if( abs level gtxflag[ n ][ 1 ] )     abs_remainder[ n ] ae(v)    AbsLevel[ xC ][ yC ] =AbsLevelPass1[ xC ][ yC ] +2 * abs remainder[ n ]   }   for( n =firstPosMode1; n >= 0; n− − ) {    xC = ( xS << log2SbW ) +DiagScanOrder[ log2SbW ][ log2SbH ][ n ] [ 0 ]    yC = ( yS << log2SbH) + DiagScanOrder[ log2SbW ][ log2SbH ][ n ] [ 1 ]    if( coded subblock flag[ xS ][ yS ] )     dec_abs_level[ n ] ae(v)    if( AbsLevel[xC ][ yC ] > 0 ) {     if( lastSigScanPosSb = = −1 )     lastSigScanPosSb = n     firstSigScanPosSb = n    }    if( ph depquant enabled flag )     QState = QStateTransTable[ QState ][ AbsLevel[xC ][ yC ] & 1 ]   }   if( ph_dep_quant_enabled_flag | |!pic_sign_data_hiding_enabled_flag | | tra nsform skipflag[x0][y0][cIdx] )    signHidden = 0   else    signHidden = (lastSigScanPosSb − firstSigScanPosSb > 3 ? 1 : 0 )   for( n = numSbCoeff− 1; n >= 0; n− − ) {    xC = ( xS << log2SbW ) + DiagScanOrder[ log2SbW][ log2SbH ][ n ] [ 0 ]    yC = ( yS << log2SbH ) + DiagScanOrder[log2SbW ][ log2SbH ][ n ] [ 1 ]    if( ( AbsLevel[ xC ][ yC ] > 0 ) &&    ( !signHidden | | ( n != firstSigScanPosSb ) ) )    coeff_sign_flag[ n ] ae(v)   }   if( ph dep quant enabled flag ) {   QState = startQStateSb    for( n = numSbCoeff − 1; n >= 0; n− − ) {    xC = ( xS << log2SbW ) + DiagScanOrder[ log2SbW ][ log2SbH ][ n ] [0 ]     yC = ( yS << log2SbH ) + DiagScanOrder[ log2SbW ][ log2SbH ][ n] [ 1 ]     if( AbsLevel[ xC ][ yC ] > 0 )      TransCoeffLevel[ x0 ][y0 ][ cIdx ][ xC ][ yC ] =        ( 2 * AbsLevel[ xC ][ yC ] − (QState > 1 ? 1 : 0 ) ) *        ( 1 − 2 * coeff sign flag[ n ] )    QState = QStateTransTable[ QState ][ AbsLevel[ xC ][ yC ] & 1 ]   }else {    sumAbsLevel = 0    for( n = numSbCoeff − 1; n >= 0; n− − ) {    xC = ( xS << log2SbW ) + DiagScanOrder[ log2SbW ][ log2SbH ][ n ] [0 ]     yC = ( yS << log2SbH ) + DiagScanOrder[ log2SbW ][ log2SbH ][ n] [ 1 ]     if( AbsLevel[ xC ][ yC ] > 0 ) {      TransCoeffLevel[ x0 ][y0 ][ cIdx ][ xC ][ yC ] =        AbsLevel[ xC ][ yC ] * ( 1 − 2 * coeffsign flag[ n ] )      if( signHidden ) {       sumAbsLevel += AbsLevel[xC ][ yC ]       if( ( n = = firstSigScanPosSb ) && ( sumAbsLevel % 2 )= = 1 ) )        TransCoeffLevel[ x0 ][ y0 ][ cIdx ][ xC ][ yC          ] = −TransCoeffLevel[ x0 ][ y0 ][ cIdx ][ xC ][ yC ]      }     }    }  }  } }

Referring to Table 18 described above, a variable signHidden indicatingwhether the SDH is applied may be derived based on a value oftransform_skip_flag. For example, when the value of transform_skip_flagis 1, the value of signHidden may be derived as 0. That is, for example,when the value of transform skip flag is 1, the SDH may not be appliedin deriving the sign of the transform coefficient of the current block.

Additionally, in this document, in order to prevent an unintended codingloss or malfunction caused by using together SDH and residual codingwhen sh_ts_residual_coding_disabled_flag=1 (that is, coding the residualsamples of transform skip blocks in the current slice with the RRC),there is provided an embodiment in which the SDH is not used in codingthe level of the transform coefficient when the value of BdpcmFlag is 1.The residual coding syntax according to the proposed embodiment may beas in the following table.

TABLE 19 Descriptor residual coding( x0, y0, log2TbWidth, log2TbHeight,cIdx ) {  if( sps_mts_enabled_flag && cu_sbt_flag && cIdx = = 0 &&   log2TbWidth = = 5 && log2TbHeight < 6 )   log2ZoTbWidth = 4  else  log2ZoTbWidth = Min( log2TbWidth, 5 )  if( sps_mts_enabled_flag &&cu_sbt_flag && cIdx = = 0 &&    log2TbWidth < 6 && log2TbHeight = = 5 )  log2ZoTbHeight = 4  else   log2ZoTbHeight = Min( log2TbHeight, 5 ) if( log2TbWidth > 0 )   last_sig_coeff_x_prefix ae(v)  if(log2TbHeight > 0 )   last_sig_coeff_y_prefix ae(v)  if( last sig coeff xprefix > 3 )   last_sig_coeff_x_suffix ae(v)  if( last sig coeff yprefix > 3 )   last_sig_coeff_y_suffix ae(v)  log2TbWidth =log2ZoTbWidth  log2TbHeight = log2ZoTbHeight  remBinsPass1 = ( ( 1 << (log2TbWidth + log2TbHeight ) ) * 7 ) >> 2  log2SbW = ( Min( log2TbWidth,log2TbHeight ) < 2 ? 1 : 2 )  log2SbH = log2SbW  if( log2TbWidth +log2TbHeight > 3 )   if( log2TbWidth < 2 ) {    log2SbW = log2TbWidth   log2SbH = 4 − log2SbW   } else if( log2TbHeight < 2 ) {    log2SbH =log2TbHeight    log2SbW = 4 − log2SbH   }  numSbCoeff = 1 << ( log2SbW +log2SbH )  lastScanPos = numSbCoeff  lastSubBlock = ( 1 << (log2TbWidth + log2TbHeight − ( log2SbW + log2Sb H ) ) ) − 1  do {   if(lastScanPos = = 0 ) {    lastScanPos = numSbCoeff    lastSubBlock− −   }  lastScanPos− −   xS = DiagScanOrder[ log2TbWidth − log2SbW ][log2TbHeight − log2SbH ]         [ lastSubBlock ][ 0 ]   yS =DiagScanOrder[ log2TbWidth − log2SbW ][ log2TbHeight − log2SbH ]        [ lastSubBlock ][ 1 ]   xC = ( xS << log2SbW ) + DiagScanOrder[log2SbW ][ log2SbH ][ lastScan Pos ][ 0 ]   yC = ( yS << log2SbH ) +DiagScanOrder[ log2SbW ][ log2SbH ][ lastScan Pos ][ 1 ]  } while( ( xC!= LastSignificantCoeffX ) | | ( yC != LastSignificantCoeffY ) )  if(lastSubBlock = = 0 && log2TbWidth >= 2 && log2TbHeight >= 2 & &   !transform skip flag[ x0 ][ y0 ][ cIdx ] && lastScanPos > 0 )  LfnstDcOnly = 0  if( ( lastSubBlock > 0 && log2TbWidth >= 2 &&log2TbHeight >= 2 ) | |    ( lastScanPos > 7 && ( log2TbWidth = = 2 | |log2TbWidth = = 3 ) & &    log2TbWidth = = log2TbHeight ) )  LfnstZeroOutSigCoeffFlag = 0  if( ( lastSubBlock > 0 | | lastScanPos >0 ) && cIdx = = 0 )   MtsDcOnly = 0  QState = 0  for( i = lastSubBlock;i >= 0; i− − ) {   startQStateSb = QState   xS = DiagScanOrder[log2TbWidth − log2SbW ][ log2TbHeight − log2SbH ]         [ i ][ 0 ]  yS = DiagScanOrder[ log2TbWidth − log2SbW ][ log2TbHeight − log2SbH ]        [ i ][ 1 ]   inferSbDcSigCoeffFlag = 0   if( i < lastSubBlock &&i > 0 ) {    coded_sub_block_flag[ xS ][ yS ] ae(v)   inferSbDcSigCoeffFlag = 1   }   if( coded_sub_block_flag[ xS ][ yS ]&& ( xS > 3 | | yS > 3 ) && cIdx = = 0 )    MtsZeroOutSigCoeffFlag = 0  firstSigScanPosSb = numSbCoeff   lastSigScanPosSb = −1   firstPosMode0= ( i = = lastSubBlock ? lastScanPos : numSbCoeff − 1 )   firstPosMode1= firstPosMode0   for( n = firstPosMode0; n >= 0 && remBinsPass1 >= 4;n− − ) {    xC = ( xS << log2SbW ) + DiagScanOrder[ log2SbW ][ log2SbH][ n ] [ 0 ]    yC = ( yS << log2SbH ) + DiagScanOrder[ log2SbW ][log2SbH ][ n ] [ 1 ]    if( coded_sub_block_flag[ xS ][ yS ] && ( n > 0| | !inferSbDcSigCoeffF lag ) &&     ( xC != LastSignificantCoeffX | |yC != Last SignificantCoeffY ) ) {     sig_coeff_flag[ xC ][ yC ] ae(v)    remBinsPass1− −     if( sig coeff flag[ xC ][ yC ] )     inferSbDcSigCoeffFlag = 0    }    if( sig coeff flag[ xC ][ yC ] ){     abs_level_gtx_flag[ n ][ 0 ] ae(v)     remBinsPass1− −     if( abslevel gtx flag[ n ][ 0 ] ) {      par_level_flag[ n ] ae(v)     remBinsPass1− −      abs_level_gtx_flag[ n ][ 1 ] ae(v)     remBinsPass1− −     }     if( lastSigScanPosSb = = −1 )     lastSigScanPosSb = n     firstSigScanPosSb = n    }   AbsLevelPass1[ xC ][ yC ] = sig_coeff_flag[ xC ][ yC ] +par_level_flag [ n ] +           abs_level_gtx_flag[ n ][ 0 ] + 2 *abs_level_gtx_flag[ n ] [ 1 ]    if( ph dep quant enabled flag )    QState = QStateTransTable[ QState ][ AbsLevelPass1[ xC ][ yC ] & 1 ]   firstPosMode1 = n − 1   }   for( n = firstPosMode0; n >firstPosMode1; n− − ) {    xC = ( xS << log2SbW ) + DiagScanOrder[log2SbW ][ log2SbH ][ n ] [ 0 ]    yC = ( yS << log2SbH ) +DiagScanOrder[ log2SbW ][ log2SbH ][ n ] [ 1 ]    if( abs level gtxflag[ n ][ 1 ] )     abs_remainder[ n ] ae(v)    AbsLevel[ xC ][ yC ] =AbsLevelPass1[ xC ][ yC ] +2 * abs remainder[ n ]   }   for( n =firstPosMode1; n >= 0; n− − ) {    xC = ( xS << log2SbW ) +DiagScanOrder[ log2SbW ][ log2SbH ][ n ] [ 0 ]    yC = ( yS << log2SbH) + DiagScanOrder[ log2SbW ][ log2SbH ][ n ] [ 1 ]    if( coded subblock flag[ xS ][ yS ] )     dec_abs_level[ n ] ae(v)    if( AbsLevel[xC ][ yC ] > 0 ) {     if( lastSigScanPosSb = = −1 )     lastSigScanPosSb = n     firstSigScanPosSb = n    }    if( ph depquant enabled flag )     QState = QStateTransTable[ QState ][ AbsLevel[xC ][ yC ] & 1 ]   }   if( ph_dep_quant_enabled_flag | |!pic_sign_data_hiding_enabled_flag | | Bd pcmFlag[ x0 ][ y0 ][ cIdx ] )   signHidden = 0   else    signHidden = ( lastSigScanPosSb −firstSigScanPosSb > 3 ? 1 : 0 )   for( n = numSbCoeff − 1; n >= 0; n− −) {    xC = ( xS << log2SbW ) + DiagScanOrder[ log2SbW ][ log2SbH ][ n ][ 0 ]    yC = ( yS << log2SbH ) + DiagScanOrder[ log2SbW ][ log2SbH ][ n] [ 1 ]    if( ( AbsLevel[ xC ][ yC ] > 0 ) &&     ( !signHidden | | ( n!= firstSigScanPosSb ) ) )     coeff_sign_flag[ n ] ae(v)   }   if( phdep quant enabled flag ) {    QState = startQStateSb    for( n =numSbCoeff − 1; n >= 0; n− − ) {     xC = ( xS << log2SbW ) +DiagScanOrder[ log2SbW ][ log2SbH ][ n ] [ 0 ]     yC = ( yS << log2SbH) + DiagScanOrder[ log2SbW ][ log2SbH ][ n ] [ 1 ]     if( AbsLevel[ xC][ yC ] > 0 )      TransCoeffLevel[ x0 ][ y0 ][ cIdx ][ xC ][ yC ] =       ( 2 * AbsLevel[ xC ][ yC ] − ( QState > 1 ? 1 : 0 ) ) *        (1 − 2 * coeff sign flag[ n ] )     QState = QStateTransTable[ QState ][AbsLevel[ xC ][ yC ] & 1 ]   } else {    sumAbsLevel = 0    for( n =numSbCoeff − 1; n >= 0; n− − ) {     xC = ( xS << log2SbW ) +DiagScanOrder[ log2SbW ][ log2SbH ][ n ] [ 0 ]     yC = ( yS << log2SbH) + DiagScanOrder[ log2SbW ][ log2SbH ][ n ] [ 1 ]     if( AbsLevel[ xC][ yC ] > 0 ) {      TransCoeffLevel[ x0 ][ y0 ][ cIdx ][ xC ][ yC ] =       AbsLevel[ xC ][ yC ] * ( 1 − 2 * coeff sign flag[ n ] )      if(signHidden ) {       sumAbsLevel += AbsLevel[ xC ][ yC ]       if( ( n == firstSigScanPosSb ) && ( sumAbsLevel % 2 ) = = 1 ) )       TransCoeffLevel[ x0 ][ y0 ][ cIdx ][ xC ][ yC           ] =−TransCoeffLevel[ x0 ][ y0 ][ cIdx ][ xC ][ yC ]      }     }    }   } } }

Referring to Table 19 above, the variable signHidden indicating whetherthe SDH is applied may be derived based on the value of the variableBdpcmFlag indicating whether the BDPCM is applied. For example, when thevalue of BdpcmFlag is 1, the value of signHidden may be derived as 0.That is, for example, when the value of BdpcmFlag is 1 (when the BDPCMis applied to the current block), the SDH may not be applied in derivingthe sign of the transform coefficient of the current block.

Referring to Table 19, when the BdpcmFlag is 1, the SDH for the TSRC isallowed if loss coding is applied, but the SDH may not be used if theBDPCM is applied.

In addition, this document proposes various embodiments related tosignaling of the above-described syntax elementsh_ts_residual_coding_disabled_flag.

For example, as described above, sincesh_ts_residual_coding_disabled_flag is a syntax element defining whetherTSRC is disabled, it may not need to be signaled when the transform skipblock is not used. That is, it may be meaningful to signal thesh_ts_residual_coding_disabled_flag only when the syntax element forwhether the transform skip block is used indicates that the transformskip block is used.

Therefore, this document proposes an embodiment in whichsh_ts_residual_coding_disabled_flag is signaled only whensps_transform_skip_enabled_flag is 1. The syntax according to thepresent embodiment is shown in the following table.

TABLE 20 Descriptor slice header( ) {  (...)  if(sps transform skipenabled flag)   sh ts residual coding disabled flag u(1)  (...) }

Referring to Table 20, when sps_transform_skip_enabled_flag is 1,sh_ts_residual_coding_disabled_flag may be signaled, while, whensps_transform_skip_enabled_flag is 0,sh_ts_residual_coding_disabled_flag may not be signaled. Here, forexample, the sps_transform_skip_enabled_flag may indicate whether atransform skip block is used. That is, for example, thesps_transform_skip_enabled_flag may indicate whether transform skip isenabled. For example, when the value of thesps_transform_skip_enabled_flag is 1, thesps_transform_skip_enabled_flag may indicate that a transform skip flag(transform_skip_flag) may be present in a transform unit syntax, while,when the value of the sps_transform_skip_enabled_flag is 0, thesps_transform_skip_enabled_flag may indicate that the transform skipflag is not present in the transform unit syntax. Meanwhile, whensh_ts_residual_coding_disabled_flag is not signaled,sh_ts_residual_coding_disabled_flag may be inferred to be 0. Inaddition, the above-described sps_transform_skip_enabled_flag may besignaled in the SPS, or may be signaled in a high-level syntax (VPS,PPS, picture header syntax, slice header syntax, or the like) orlow-level syntax (slice data syntax, coding unit syntax, transform unitsyntax, or the like) other than SPS. Also, it may be signaled beforesh_ts_residual_coding_disabled_flag.

Additionally, this document proposes an embodiment combining theembodiments described above in connection with signaling ofsh_ts_residual_coding_disabled_flag. For example, an embodiment ofsignaling sh_ts_residual_coding_disabled_flag may be proposed as shownin the following table.

TABLE 21 Descriptor slice header( ) {  (...)  if(!pic_sign_data_hiding_enabled_flag &&  sps_transform_skip_enabled_flag )  sh ts residual coding disabled flag u(1)  (...) }

Referring to Table 21, when sps_transform_skip_enabled_flag is 1 andpic_sign_data_hiding_enabled_flag is 0,sh_ts_residual_coding_disabled_flag may be signaled, while otherwisesh_ts_residual_coding_disabled_flag may not be signaled. Meanwhile, whensh_ts_residual_coding_disabled_flag is not signaled,sh_ts_residual_coding_disabled_flag may be inferred to be 0.

Alternatively, for example, an embodiment of signalingsh_ts_residual_coding_disabled_flag may be proposed as shown in thefollowing table.

TABLE 22 Descriptor picture header structure( ) {  (...)   ph dep quantenabled flag  if( !pic sign data hiding enabled flag || sps  transformskip enabled flag)    ph ts residual coding disabled flag u(1)  (...) }

Referring to Table 22, when pic_sign_data_hiding_enabled_flag is 0 orsps_transform_skip_enabled_flag is 1,sh_ts_residual_coding_disabled_flag may be signaled, while otherwisesh_ts_residual_coding_disabled_flag may not be signaled. Meanwhile, whensh_ts_residual_coding_disabled_flag is not signaled,sh_ts_residual_coding_disabled_flag may be inferred to be 0.

Also, for example, according to this embodiment, a method of signalingthe syntax elements ph_dep_quant_enabled_flag andsh_ts_residual_coding_disabled_flag in the same high-level syntax orlow-level syntax may be proposed. For example, referring to Table 22above, both ph_dep_quant_enabled_flag andsh_ts_residual_coding_disabled_flag may be signaled in the pictureheader syntax. In this case, the sh_ts_residual_coding_disabled_flag maybe referred to as ph_ts_residual_coding_disabled_flag. Meanwhile, theph_dep_quant_enabled_flag may be a flag indicating whether dependentquantization is enabled. For example, ph_dep_quant_enabled_flag mayindicate whether dependent quantization is enabled. That is, forexample, ph_dep_quant_enabled_flag may indicate whether dependentquantization is enabled for blocks of pictures in a sequence. Forexample, ph_dep_quant_enabled_flag may indicate whether a dependentquantization used flag indicating whether dependent quantization is usedfor the current slice may be present. For example, theph_dep_quant_enabled_flag whose value is 1 may indicate that thedependent quantization is enabled, while the ph_dep_quant_enabled_flagwhose value is 0 may indicate that the dependent quantization is notenabled. Also, for example, the ph_dep_quant_enabled_flag may be calledsps_dep_quant_enabled_flag or sh_dep_quant_enabled_flag according to asignaled syntax.

Alternatively, for example, an embodiment of signalingsh_ts_residual_coding_disabled_flag may be proposed as shown in thefollowing table.

TABLE 23 Descriptor picture header structure( ) {  (...)   ph dep quantenabled flag  if( !pic_sign_data_hiding_enabled_flag && sps_transform_skip_enabled_flag )   ph_ts_residual_coding_disabled_flag u(1)  (...) }

Referring to Table 23, when pic_sign_data_hiding_enabled_flag is 0 andsps_transform_skip_enabled_flag is 1,sh_ts_residual_coding_disabled_flag may be signaled, while otherwisesh_ts_residual_coding_disabled_flag may not be signaled. Meanwhile, whensh_ts_residual_coding_disabled_flag is not signaled,sh_ts_residual_coding_disabled_flag may be inferred to be 0. Also, forexample, referring to Table 23 above, both ph_dep_quant_enabled_flag andsh_ts_residual_coding_disabled_flag may be signaled in the pictureheader syntax. In this case, the sh_ts_residual_coding_disabled_flag maybe referred to as ph_ts_residual_coding_disabled_flag.

In addition, this document proposes an embodiment in which theabove-described syntax elements ph_dep_quant_enabled_flag,pic_sign_data_hiding_enabled_flag and/orsh_ts_residual_coding_disabled_flag are signaled in the same high levelsyntax (VPS, SPS, PPS, picture header, slice header, or the like) or lowlevel syntax (slice data, coding unit, transform unit, or the like).

For example, as shown in the following table, an embodiment in whichboth pic_sign_data_hiding_enabled_flag andsh_ts_residual_coding_disabled_flag are signaled in picture headersyntax may be proposed.

TABLE 24 Descriptor picture header structure( ) {  (...)   if( sps signdata hiding enabled flag )    pic sign data hiding enabled flag u(1) if( !pic sign data hiding enabled flag )    ph ts residual codingdisabled flag u(1)  (...) }

In this case, the sh_ts_residual_coding_disabled_flag may be referred toas ph_ts_residual_coding_disabled_flag.

According to this embodiment, a syntax element (i.e.,sh_ts_residual_coding_disabled_flag) indicating whether residual coding(i.e., TSRC) for the transform skip block is enabled may be signaledonly when the value of the syntax element (ie,pic_sign_data_hiding_enabled_flag) indicating whether SDH is enabled inHLS is 0. For example, referring to Table 24,pic_sign_data_hiding_enabled_flag may be signaled in picture headersyntax, and when the value of pic_sign_data_hiding_enabled_flag is 0,ph_ts_residual_coding_disabled_flag may be signaled in picture headersyntax. Meanwhile, for example, when the value ofpic_sign_data_hiding_enabled_flag is 1,ph_ts_residual_coding_disabled_flag may not be signaled. Whensh_ts_residual_coding_disabled_flag is not signaled,sh_ts_residual_coding_disabled_flag may be inferred to be 0. Also, whenthe value of sps_sign_data_hiding_enabled_flag is 1,pic_sign_data_hiding_enabled_flag may be signaled in picture headersyntax.

The embodiment according to Table 24 described above is only an example,and the two syntax elements may be signaled in high-level syntax (VPS,SPS, PPS, slice header, or the like) or low-level syntax (slice data,coding unit, transform unit, or the like) other than the picture header.

Alternatively, for example, as shown in the following table, there maybe provided an embodiment in which a syntax element indicating whetherSDH is enabled is signaled only when the value of the syntax elementindicating whether residual coding (i.e., TSRC) for the transform skipblock is enabled is 0 (i.e., when TSRC is enabled).

TABLE 25 Descriptor picture header structure( ) {  (...) ph_ts_residual_coding_disabled_flag  if( !ph ts residual codingdisabled flag )   pic_sign_data_hiding_enabled_flag u(1)  (...) }

Referring to Table 25, when the value ofph_ts_residual_coding_disabled_flag is 0,pic_sign_data_hiding_enabled_flag may be signaled in the picture headersyntax. Meanwhile, for example, when the value ofph_ts_residual_coding_disabled_flag is 1,pic_sign_data_hiding_enabled_flag may not be signaled. Also, forexample, when pic_sign_data_hiding_enabled_flag is not signaled,pic_sign_data_hiding_enabled_flag may be inferred to be 0 in thedecoding apparatus.

The embodiment according to Table 25 described above is only an example,and the two syntax elements may be signaled in high-level syntax (VPS,SPS, PPS, slice header, or the like) or low-level syntax (slice data,coding unit, transform unit, or the like) other than the picture header.

Alternatively, for example, methods for restrictingpic_sign_data_hiding_enabled_flag and/or ph_dep_quant_enabled_flag basedon ph_ts_residual_coding_disabled_flag may be proposed.

For example, as shown in the following table, there may be provided anembodiment in which pic_sign_data_hiding_enabled_flag andph_dep_quant_enabled_flag are signaled only when the value ofph_ts_residual_coding_disabled_flag is 0.

TABLE 26 Descriptor picture header structure( ) {  (...) ph_ts_residual_coding_disabled_flag  if( !ph ts residual codingdisabled flag ) {   pic_sign_data_hiding_enabled_flag u(1)  ph_dep_quant_enabled_flag u(1)  }  (...) }

Referring to Table 26, when the value ofph_ts_residual_coding_disabled_flag is 0,pic_sign_data_hiding_enabled_flag and ph_dep_quant_enabled_flag may besignaled in picture header syntax. Meanwhile, for example, when thevalue of ph_ts_residual_coding_disabled_flag is 1,pic_sign_data_hiding_enabled_flag and ph_dep_quant_enabled_flag may notbe signaled. Also, for example, when pic_sign_data_hiding_enabled_flagand ph_dep_quant_enabled_flag are not signaled,pic_sign_data_hiding_enabled_flag and ph_dep_quant_enabled_flag may beinferred to be 0 in the decoding apparatus.

Also, for example, referring to Table 26 above, ph_ts_residual_codingdisabled flag, pic_sign_data_hiding_enabled_flag, andph_dep_quant_enabled_flag may all be signaled in the picture headersyntax.

Additionally, this document proposes an embodiment combining theembodiments described above in connection with signaling ofsh_ts_residual_coding_disabled_flag. For example, an embodiment ofsignaling sh_ts_residual_coding_disabled_flag may be proposed as shownin the following table.

TABLE 27 Descriptor picture header structure( ) {  (...)   if( sps signdata hiding enabled flag)    pic_sign_data_hiding_enabled_flag u(1)  if(!pic sign data hiding enabled flag | | sps  transform skip enabled flag)   ph_ts_residual_coding_disabled_flag u(1)  (...) }

Referring to Table 27, when pic_sign_data_hiding_enabled_flag is 0 orsps_transform_skip_enabled_flag is 1,ph_ts_residual_coding_disabled_flag may be signaled, while otherwiseph_ts_residual_coding_disabled_flag may not be signaled. Meanwhile, whenph_ts_residual_coding_disabled_flag is not signaled,ph_ts_residual_coding_disabled_flag may be inferred to be 0 in thedecoding apparatus. Also, when the value ofsps_sign_data_hiding_enabled_flag is 1,pic_sign_data_hiding_enabled_flag may be signaled in picture headersyntax.

Alternatively, for example, an embodiment of signalingsh_ts_residual_coding_disabled_flag may be proposed as shown in thefollowing table.

TABLE 28 Descriptor picture header structure( ) {  (...)   if( sps signdata hiding enabled flag)    pic_sign_data_hiding_enabled_flag u(1)  if(!pic_sign_data_hiding_enabled_flag &&  sps_transform_skip_enabled_flag )   ph_ts_residual_coding_disabled_flag u(1)  (...) }

Referring to Table 28, when pie sign data hiding enabled flag is 0 andsps_transform_skip_enabled_flag is 1,ph_ts_residual_coding_disabled_flag may be signaled, while otherwiseph_ts_residual_coding_disabled_flag may not be signaled. Meanwhile, whenph_ts_residual_coding_disabled_flag is not signaled,ph_ts_residual_coding_disabled_flag may be inferred to be 0 in thedecoding apparatus. Also, when the value ofsps_sign_data_hiding_enabled_flag is 1,pic_sign_data_hiding_enabled_flag may be signaled in picture headersyntax.

Alternatively, for example, an embodiment of signalingsh_ts_residual_coding_disabled_flag may be proposed as shown in thefollowing table.

TABLE 29 Descriptor picture header structure( ) {  (...)   if(spstransform skip enabled flag)    ph ts residual coding disabled flag  if(!ph ts residual coding disabled flag )     pic sign data hiding enabledflag u(1)  (...) }

Referring to Table 29, when sps_transform_skip_enabled_flag is 1,ph_ts_residual_coding_disabled_flag may be signaled, while otherwiseph_ts_residual_coding_disabled_flag may not be signaled. Also, referringto Table 29, when ph_ts_residual_coding_disabled_flag is 0,pic_sign_data_hiding_enabled_flag may be signaled, while otherwisepic_sign_data_hiding_enabled_flag may not be signaled. Meanwhile, whenph_ts_residual_coding_disabled_flag is not signaled,ph_ts_residual_coding_disabled_flag may be inferred to be 0 in thedecoding apparatus. Also, when pic_sign_data_hiding_enabled_flag is notsignaled, pic_sign_data_hiding_enabled_flag may be inferred to be 0 inthe decoding apparatus.

Alternatively, for example, an embodiment of signalingsh_ts_residual_coding_disabled_flag may be proposed as shown in thefollowing table.

TABLE 30 Descriptor picture header structure( ) {  (...)   if(spstransform skip enabled flag)    ph_ts_residual_coding_disabled_flag  if( !ph ts residual coding disabled flag ){    pic sign data hidingenabled flag u(1)    ph dep quant enabled flag u(1)  }  (...) }

Referring to Table 30, when sps_transform_skip_enabled_flag is 1,ph_ts_residual_coding_disabled_flag may be signaled, while otherwiseph_ts_residual_coding_disabled_flag may not be signaled. In addition,referring to Table 30, when ph_ts_residual_coding_disabled_flag is 0,pic sign data hiding enabled flag and ph_dep_quant_enabled_flag may besignaled, while otherwise pic_sign_data_hiding_enabled_flag andph_dep_quant_enabled_flag may not be signaled. Meanwhile, whenph_ts_residual_coding_disabled_flag is not signaled,ph_ts_residual_coding_disabled_flag may be inferred to be 0 in thedecoding apparatus. Also, when pic_sign_data_hiding_enabled_flag andph_dep_quant_enabled_flag are not signaled,pic_sign_data_hiding_enabled_flag and ph_dep_quant_enabled_flag may beinferred to be 0 in the decoding apparatus.

Meanwhile, as described above, the information (syntax element) in thesyntax table disclosed in this document may be included in theimage/video information, and may be configured/encoded in the encodingapparatus and transmitted to the decoding apparatus in the form of abitstream. The decoding apparatus may parse/decode information (syntaxelement) in the corresponding syntax table. The decoding apparatus mayperform a block/image/video reconstruction process based on the decodedinformation.

FIG. 12 briefly illustrates an image encoding method performed by anencoding apparatus according to the present disclosure. The methoddisclosed in FIG. 12 may be performed by the encoding apparatusdisclosed in FIG. 2 . Specifically, for example, S900 of FIG. 9 may beperformed by the predictor of the encoding apparatus, S910 of FIG. 9 maybe performed by the residual processor of the encoding apparatus, andS920 to S960 of FIG. 9 may be performed by the entropy encoder of theencoding apparatus. Additionally, although not shown, the process ofgenerating the reconstructed sample and the reconstructed picture forthe current block based on the residual sample and the prediction samplefor the current block may be performed by the adder of the encodingapparatus.

The encoding apparatus generates a reconstructed picture for a currentslice (S1200). The encoding apparatus may derive a prediction sample anda residual sample for a current block of the current slice, and maygenerate a reconstructed sample/a reconstructed picture for the currentblock based on the prediction sample and the residual sample.

Specifically, for example, the encoding apparatus may by perform on thecurrent block in the current slice to derive a prediction sample of thecurrent block. For example, the encoding apparatus may derive aprediction sample of the current block by performing intra prediction orinter prediction on the current block. For example, the encodingapparatus may determine whether to perform inter prediction or intraprediction on the current block, may determine a specific interprediction mode or a specific intra prediction mode based on RD cost,and may derive the prediction samples of the current block based on thedetermined prediction mode.

For example, the encoding apparatus may derive the inter prediction modeand the motion information of the current block and generate theprediction samples of the current block. Here, an inter prediction modedetermining process, a motion information deriving process, and ageneration process of the prediction samples may be simultaneouslyperformed and any one process may be performed earlier than otherprocess. For example, the inter-prediction unit of the encodingapparatus may include a prediction mode determination unit, a motioninformation derivation unit, and a prediction sample derivation unit,and the prediction mode determination unit may determine the predictionmode for the current block, the motion information derivation unit mayderive the motion information of the current block, and the predictionsample derivation unit may derive the prediction samples of the currentblock. For example, the inter-prediction unit of the encoding apparatusmay search a block similar to the current block in a predetermined area(search area) of reference pictures through motion estimation and derivea reference block in which a difference from the current block isminimum or is equal to or less than a predetermined criterion. Areference picture index indicating a reference picture at which thereference block is positioned may be derived based thereon and a motionvector may be derived based on a difference in location between thereference block and the current block. The encoding apparatus maydetermine a mode applied to the current block among various predictionmodes. The encoding apparatus may compare RD cost for the variousprediction modes and determine an optimal prediction mode for thecurrent block.

For example, the encoding apparatus may configure a motion informationcandidate list for the current block and derive a reference block inwhich a difference from the current block is minimum or is equal to orless than a predetermined criterion among reference blocks indicated bymotion information candidates included in the motion informationcandidate list. In this case, a motion information candidate associatedwith the derived reference block may be selected and the motioninformation of the current block may be derived based on the motioninformation of the selected motion information candidate.

Also, for example, the encoding apparatus may derive the residual sampleof the current block based on the prediction sample. For example,encoding apparatus may derive the residual samples for the current blockthrough the subtraction of the prediction samples with the originalsamples for the current block.

Then, for example, the encoding apparatus may generate a reconstructedsample and a reconstructed picture for the current block based on aresidual sample and a prediction sample for the current block. Forexample, the encoding apparatus may generate the reconstructed sample byadding the prediction sample and the residual sample.

The encoding apparatus encodes image information for the current slice(S1210). The encoding apparatus may generate and encode the imageinformation for the current slice.

For example, the encoding apparatus may encode a sign data hidingenabled flag for whether sign data hiding is enabled for the currentslice. The encoding apparatus may encode a sign data hiding enabled flagfor whether sign data hiding is enabled for the current slice. The imageinformation may include a sign data hiding enabled flag. For example,the encoding apparatus may determine whether sign data hiding is enabledfor blocks of pictures in a sequence, an may encode a sign data hidingenabled flag for whether sign data hiding is enabled. For example, thesign data hiding enabled flag may be a flag for whether sign data hidingis enabled. For example, the sign data hiding enabled flag may indicatewhether sign data hiding is enabled. That is, for example, the sign datahiding enabled flag may indicate whether sign data hiding is enabled forblocks of pictures in a sequence. For example, sign data hiding enabledflag may indicate whether a sign data hiding used flag indicatingwhether sign data hiding is used for the current slice may be present.For example, the sign data hiding enabled flag whose value is 1 mayindicate that the sign data hiding is enabled, while the sign datahiding enabled flag whose value is 0 may indicate that the sign datahiding is not enabled. For example, the sign data hiding enabled flagwhose value is 1 may indicate that a sign data hiding used flag may bepresent, while the sign data hiding enabled flag whose value is 0 mayindicate that a sign data hiding used flag is not present. Also, forexample, the sign data hiding enabled flag may be signaled in a sequenceparameter set (SPS) syntax. Alternatively, for example, the sign datahiding enabled flag may be signaled in a picture header syntax or aslice header syntax. The syntax element of the sign data hiding enabledflag may be the above-described sps_sign_data_hiding_enabled_flag.Alternatively, the syntax element of the sign data hiding enabled flagmay be the above-described sh_sign_data_hiding_enabled_flag.

Then, for example, the encoding apparatus may encode a Transform SkipResidual Coding (TSRC) enabled flag for whether TSRC is enabled for atransform skip block in the current slice based on the sign data hidingenabled flag. The image information may include a TSRC enabled flag.

For example, the encoding apparatus may encode the TSRC enabled flagbased on the sign data hiding enabled flag. For example, the TSRCenabled flag may be encoded based on the sign data hiding enabled flagwhose value is 0. That is, for example, when the value of the sign datahiding enabled flag is 0 (i.e., when the sign data hiding enabled flagindicates that sign data hiding is not enabled), the TSRC enabled flagmay be encoded. In other words, for example, when the value of the signdata hiding enabled flag is 0 (i.e., when the sign data hiding enabledflag indicates that sign data hiding is not enabled), the TSRC enabledflag may be signaled. Also, for example, when the value of the sign datahiding enabled flag is 1, the TSRC enabled flag may not be encoded, andthe value of the TSRC enabled flag may be derived as 0 in the decodingapparatus. That is, for example, when the value of the sign data hidingenabled flag is 1, the TSRC enabled flag may not be signaled, and thevalue of the TSRC enabled flag may be derived as 0 in the decodingapparatus.

Here, for example, the TSRC enabled flag may be a flag for whether TSRCis enabled. That is, for example, the TSRC enabled flag may be a flagindicating whether TSRC is enabled for blocks in a slice. In otherwords, for example, the TSRC enabled flag may be a flag indicatingwhether TSRC is enabled for a transform skip block in a slice. Forexample, the TSRC enabled flag whose value is 1 may indicate that theTSRC is not enabled, and the TSRC enabled flag whose value is 0 mayindicate that the TSRC is enabled. Also, for example, the TSRC enabledflag may be signaled in a slice header syntax. The syntax element of theTSRC enabled flag may be the above-describedsh_ts_residual_coding_disabled_flag. The TSRC enabled flag may bereferred to as a TSRC disabled flag.

Meanwhile, for example, the encoding apparatus may determine whetherdependent quantization is enabled for blocks of pictures in a sequence,and may encode a dependent quantization enabled flag for whetherdependent quantization is enabled. The image information may include thedependent quantization enabled flag. For example, the dependentquantization enabled flag may be a flag for whether dependentquantization is enabled. For example, the dependent quantization enabledflag may indicate whether dependent quantization is enabled. That is,for example, the dependent quantization enabled flag may indicatewhether dependent quantization is enabled for blocks of pictures in asequence. For example, dependent quantization enabled flag may indicatewhether a dependent quantization used flag indicating whether dependentquantization is used for the current slice may be present. For example,the dependent quantization enabled flag whose value is 1 may indicatethat the dependent quantization is enabled, and the dependentquantization enabled flag whose value is 0 may indicate that thedependent quantization is not enabled. Also, for example, the dependentquantization enabled flag may be signaled in an SPS syntax, a sliceheader syntax or the like. The syntax element of the dependentquantization enabled flag may be the above-describedsps_dep_quant_enabled_flag.

Also, for example, the encoding apparatus may encode a transform skipenabled flag for whether transform skip is enabled for the currentslice. The image information may include a transform skip enabled flag.For example, the encoding apparatus may determine whether transform skipis enabled for blocks of pictures in a sequence, and may encode atransform skip enabled flag for whether transform skip is enabled. Forexample, the transform skip enabled flag may be a flag for whethertransform skip is enabled. For example, the transform skip enabled flagmay indicate whether transform skip is enabled. That is, for example,the transform skip enabled flag may indicate whether transform skip isenabled for blocks of pictures in a sequence. For example, the transformskip enabled flag may indicate whether a transform skip flag may bepresent. For example, the transform skip enabled flag whose value is 1may indicate that the transform skip is enabled, and the transform skipenabled flag whose value is 0 may indicate that the transform skip isnot enabled. That is, for example, the transform skip enabled flag whosevalue is 1 may indicate that the transform skip flag may be present, andthe transform skip enabled flag whose value is 0 may indicate that thetransform skip flag is not present. Also, for example, the transformskip enabled flag may be signaled in a sequence parameter set (SPS)syntax. The syntax element of the transform skip enabled flag may be theabove-described sps_transform_skip_enabled_flag.

Also, for example, the TSRC enabled flag may be encoded based on thesign data hiding enabled flag and/or the transform skip enabled flag.For example, the TSRC enabled flag may be encoded based on the sign datahiding enabled flag whose value is 0, and the transform skip enabledflag whose value is 1. That is, for example, when the value of the signdata hiding enabled flag is 0 (that is, the sign data hiding enabledflag indicates that sign data hiding is not enabled), and the value ofthe transform skip enabled flag is 1 (that is, when the transform skipenabled flag indicates that the transform skip is enabled), the TSRCenabled flag may be encoded (or signaled). Also, for example, when thevalue of the transform skip enabled flag is 0, the TSRC enabled flag maynot be encoded, and the value of the TSRC enabled flag may be derived as0. That is, for example, when the value of the transform skip enabledflag is 0, the TSRC enabled flag may not be signaled, and the value ofthe TSRC enabled flag may be derived as 0.

Also, for example, the encoding apparatus may encode predictioninformation for the current block in the current slice. The imageinformation may include prediction information for the current block.For example, the prediction information may include prediction modeinformation as information related to the prediction procedure.

Also, for example, the encoding apparatus may encode residualinformation for the current block in the current slice. For example, theencoding apparatus may encode the residual information for the currentblock based on the TSRC enabled flag. The encoding apparatus may encoderesidual information for the current block based on the TSRC enabledflag.

For example, the encoding apparatus may determine a residual codingsyntax for the current block based on the TSRC enabled flag. Forexample, the encoding apparatus may determine a residual coding syntaxfor the current block as one of the Regular Residual Coding (RRC) syntaxand Transform Skip Residual Coding (TSRC) syntax based on the TSRCenabled flag. The RRC syntax may indicate a syntax according to RRC, andthe TSRC syntax may indicate a syntax according to TSRC.

For example, the residual coding syntax for the current block may bedetermined as the regular residual coding (RRC) syntax based on the TSRCenabled flag whose value is 1. In this case, for example, a transformskip flag for whether the current block is transform-skipped may beencoded, and the value of the transform skip flag may be 1. For example,the image information may include a transform skip flag for the currentblock. The transform skip flag may indicate whether the current block istransform-skipped. That is, the transform skip flag may indicate whethera transform is applied to transform coefficients of the current block.The syntax element representing the transform skip flag may be theabove-described transform_skip_flag. For example, when the value of thetransform skip flag is 1, the transform skip flag may indicate thattransform is not applied to the current block (i.e., transform-skipped),while, when the value of the transform skip flag is 0, the transformskip flag may indicate that transform is applied to the current block.For example, when the current block is a transform skip block, the valueof the transform skip flag for the current block may be 1.

Also, for example, the residual coding syntax for the current block maybe determined as the transform skip residual coding (TSRC) syntax basedon the TSRC enabled flag whose value is 0. Also, for example, thetransform skip flag for whether the current block is transform-skippedmay be encoded, and the residual coding syntax for the current block maybe determined as the transform skip residual coding (TSRC) syntax basedon the transform skip flag whose value is 1 and the TSRC enabled flagwhose value is 0. Also, for example, the transform skip flag for whetherthe current block is transform-skipped may be encoded, and the residualcoding syntax for the current block may be determined as the RegularResidual Coding (RRC) syntax based on the transform skip flag whosevalue is 0 and the TSRC enabled flag whose value is 0.

Then, for example, the encoding apparatus may encode residualinformation of the determined residual coding syntax for the currentblock. The encoding apparatus may encode residual information of thedetermined residual coding syntax for the residual sample of the currentblock. For example, residual information of the regular residual coding(RRC) syntax for the current block may be encoded based on the TSRCenabled flag whose value is 1, and residual information of the TSRCsyntax for the current block may be encoded based on the TSRC enabledflag whose value is 0. The image information may include residualinformation.

Specifically, for example, the encoding apparatus may derive transformcoefficients of the current block based on the residual samples. Forexample, the encoding apparatus may determine whether a transform isapplied to the current block. That is, the encoding apparatus maydetermine whether a transform is applied to the residual samples of thecurrent block. The encoding apparatus may determine whether to apply thetransform to the current block in consideration of coding efficiency.For example, the encoding apparatus may determine that no transform isapplied to the current block. Meanwhile, a block to which the transformis not applied may be referred to as a transform skip block.

When transform is not applied to the current block, that is, whentransform is not applied to the residual samples, the encoding apparatusmay derive the derived residual samples as transform coefficients of thecurrent block. In addition, when transform is applied to the currentblock, that is, when transform is applied to the residual samples, theencoding apparatus may perform transform on the residual samples toderive transform coefficients of the current block. The current blockmay include a plurality of sub-blocks or Coefficient Groups (CGs). Inaddition, the size of the subblock of the current block may be 4×4 sizeor 2×2 size. That is, the subblock of the current block may include upto 16 non-zero transform coefficients or up to 4 non-zero transformcoefficients. Here, the current block may be a coding block (CB) or atransform block (TB). Also, the transform coefficient may be referred toas a residual coefficient.

For example, when the residual coding syntax for the current block isdetermined as the RRC syntax, the encoding apparatus may encode residualinformation of the RRC syntax for the current block. For example, theresidual information of the RRC syntax may include the syntax elementsshown in Table 2 above.

For example, the residual information of the RRC syntax may includesyntax elements for transform coefficients of a current block. Here, thetransform coefficient may be referred to as a residual coefficient.

For example, the syntax elements may include syntax elements such aslast_sig_coeff_x_prefix, last_sig_coeff_y_prefix,last_sig_coeff_x_suffix, last_sig_coeff_y_suffix, sb_coded_flag,sig_coeff_flag, abs_level_gt1_flag, par_level_flag, abs_level_gtX_flag,abs_remainder, dec_abs_level, and/or coeff_sign_flag.

Specifically, for example, the syntax elements may include positioninformation indicating the position of the last non-zero transformcoefficient in the residual coefficient array of the current block. Thatis, the syntax elements may include position information indicating theposition of the last non-zero transform coefficient in a scanning orderof the current block. The position information may include informationindicating a prefix of a column position of the last non-zero transformcoefficient, information indicating a prefix of a row position of thelast non-zero transform coefficient, information indicating a suffix ofa column position of the last non-zero transform coefficient, andinformation indicating a suffix of a row position of the last non-zerotransform coefficient. The syntax elements for the location informationmay be last_sig_coeff_x_prefix, last_sig_coeff_y_prefix,last_sig_coeff_x_suffix, and last_sig_coeff_y_suffix. Meanwhile, thenon-zero transform coefficient may be referred to as a significantcoefficient.

Also, for example, the syntax elements may include a coded subblock flagindicating whether a subblock of the current block includes a non-zerotransform coefficient; a significant coefficient flag indicating whetherthe transform coefficient of the current block is non-zero transformcoefficient; a first coefficient level flag for whether the coefficientlevel for the transform coefficient is greater than a first threshold; aparity level flag for parity of the coefficient level; and/or a secondcoefficient level flag for whether the coefficient level of thetransform coefficient is greater than a second threshold. Here, thecoded sub-block flag may be sb_coded_flag or coded_sub_block_flag; thesignificant coefficient flag may be sig_coeff_flag; the firstcoefficient level flag may be abs_level_gt1_flag or abs_level_gtx_flag;the parity level flag may be par_level_flag; and the second coefficientlevel flag may be abs_level_gt3_flag or abs_level_gtx_flag.

Also, for example, the syntax elements may include information relatedto the coefficient value for value of transform coefficient of thecurrent block. The coefficient value related information may be absremainder and/or dec abs level.

Also, for example, the syntax elements may include a sign flagindicating a sign of the transform coefficient. The sign flag may becoeff_sign_flag.

Meanwhile, for example, when the sign data hiding is applied to thecurrent block, the sign flag of the first significant transformcoefficient of the current coefficient group (CG) in the current blockmay not be encoded and signaled. That is, for example, when the signdata hiding is applied to the current block, the syntax elements may notinclude a sign flag indicating a sign of the first significant transformcoefficient. Meanwhile, for example, whether the sign data hiding isapplied to the current block may be derived based on the sign datahiding enabled flag, and/or the position of the first significanttransform coefficient and the position of the last significant transformcoefficient of the current CG of the current block. For example, whenthe value of the sign data hiding enabled flag is 1, and the valueobtained by subtracting the first significant transform coefficientposition from the last significant transform coefficient position isgreater than 3 (that is, when the value of the sign data hiding enabledflag is 1, and the number of significant transform coefficients in thecurrent CG is greater than 3), the sign data hiding may be applied tothe current CG of the current block.

Additionally, for example, when the residual coding syntax for thecurrent block is determined as the TSRC syntax, the encoding apparatusmay encode residual information of the TSRC syntax for the currentblock. For example, the residual information of the TSRC syntax mayinclude the syntax elements shown in Table 3 above.

For example, the residual information of the TSRC syntax may includesyntax elements for transform coefficients of a current block. Here, thetransform coefficient may be referred to as a residual coefficient.

For example, the syntax elements may include context coded syntaxelements and/or bypass coded syntax elements for a transformcoefficient. The syntax elements may include syntax elements such assig_coeff_flag, coeff_sign_flag, abs_level_gt1_flag, par_level_flag,abs_level_gtX_flag and/or abs_remainder.

For example, the context-coded syntax elements for the transformcoefficient may include a significant coefficient flag indicatingwhether the transform coefficient is a non-zero transform coefficient; asign flag indicating a sign for the transform coefficient; a firstcoefficient level flag for whether the coefficient level for thetransform coefficient is greater than a first threshold; and/or paritylevel flag for parity of the coefficient level for the transformcoefficient. In addition, for example, the context-coded syntax elementsmay include a second coefficient level flag for whether the coefficientlevel of the transform coefficient is greater than a second threshold; athird coefficient level flag for whether the coefficient level of thetransform coefficient is greater than a third threshold; a fourthcoefficient level flag for whether the coefficient level of thetransform coefficient is greater than a fourth threshold; and/or a fifthcoefficient level flag for whether the coefficient level of thetransform coefficient is greater than a fifth threshold. Here, thesignificant coefficient flag may be sig_coeff_flag; the sign flag may becoeff_sign_flag; the first coefficient level flag may beabs_level_gt1_flag; and the parity level flag may be par_level_flag. Inaddition, the second coefficient level flag may be abs_level_gt3_flag orabs_level_gtx_flag; the third coefficient level flag may beabs_level_gt5_flag or abs_level_gtx_flag; the fourth coefficient levelflag may be abs_level_gt7_flag or abs_level_gtx_flag; and the fifthcoefficient level flag may be abs_level_gt9_flag or abs_level_gtx_flag.

Also, for example, the syntax elements bypass-coded for the transformcoefficient may include coefficient level information for the value (orcoefficient level) of the transform coefficient, and/or a sign flagindicating a sign for the transform coefficient. The coefficient levelinformation may be abs_remainder and/or dec_abs_level, and the sign flagmay be coeff_sign_flag.

Also, for example, the encoding apparatus may generate a bitstreamincluding the sign data hiding enabled flag, the TSRC enabled flag, theprediction information and/or the residual information. That is, forexample, the encoding apparatus may output, as a bitstream, imageinformation including the sign data hiding enabled flag, the TSRCenabled flag, the prediction information and/or the residualinformation. The bitstream may include the sign data hiding enabledflag, the TSRC enabled flag, the prediction information and/or theresidual information. In addition, the bitstream may further include thedependent quantization enabled flag and/or the transform skip enabledflag.

Meanwhile, the bitstream may be transmitted to the decoding apparatusthrough a network or a (digital) storage medium. Here, the network mayinclude a broadcast network, a communication network and/or the like,and the digital storage medium may include various storage media, suchas a universal serial bus (USB), secure digital (SD), a compact disk(CD), a digital video disk (DVD), Blu-ray, a hard disk drive (HDD), asolid state drive (SSD), and the like.

FIG. 13 briefly illustrates an encoding apparatus for performing animage encoding method according to the present disclosure. The methoddisclosed in FIG. 12 may be performed by the encoding apparatusdisclosed in FIG. 13 . Specifically, for example, the residual processorof the encoding apparatus of FIG. 13 may perform S1200 in FIG. 12 , andthe entropy encoder of the encoding apparatus of FIG. 13 may performS1210 in FIG. 12 . Additionally, although not shown, the process ofgenerating the reconstructed sample and the reconstructed picture forthe current block based on the residual sample and the prediction samplefor the current block in the current slice may be performed by the adderof the encoding apparatus.

FIG. 14 briefly illustrates an image decoding method performed by adecoding apparatus according to the present disclosure. The methoddisclosed in FIG. 14 may be performed by the decoding apparatusdisclosed in FIG. 3 . Specifically, for example, S1400 of FIG. 14 may beperformed by the entropy decoder of the decoding apparatus, S1410 ofFIG. 14 may be performed by the residual processor of the decodingapparatus. In addition, although not shown, the process of receivingprediction information for the current block may be performed by anentropy decoder of the decoding apparatus, and the process of derivingthe prediction sample of the current block based on the predictioninformation may be performed by the predictor of the decoding apparatus.

The decoding apparatus obtains image information (S1400). The decodingapparatus may obtain image information through a bitstream.

For example, the decoding apparatus may obtain a sign data hidingenabled flag for whether sign data hiding is enabled for a currentslice. The decoding apparatus may obtain image information including thesign data hiding enabled flag through the bitstream. The imageinformation may include the sign data hiding enabled flag. For example,the sign data hiding enabled flag may be a flag for whether sign datahiding is enabled. For example, the sign data hiding enabled flag mayindicate whether sign data hiding is enabled. That is, for example, thesign data hiding enabled flag may indicate whether sign data hiding isenabled for blocks of pictures in a sequence. For example, sign datahiding enabled flag may indicate whether a sign data hiding used flagindicating whether sign data hiding is used for the current slice may bepresent. For example, the sign data hiding enabled flag whose value is 1may indicate that the sign data hiding is enabled, while the sign datahiding enabled flag whose value is 0 may indicate that the sign datahiding is not enabled. For example, the sign data hiding enabled flagwhose value is 1 may indicate that a sign data hiding used flag may bepresent, while the sign data hiding enabled flag whose value is 0 mayindicate that a sign data hiding used flag is not present. Also, forexample, the sign data hiding enabled flag may be signaled in a sequenceparameter set (SPS) syntax. Alternatively, for example, the sign datahiding enabled flag may be signaled in a picture header syntax or aslice header syntax. The syntax element of the sign data hiding enabledflag may be the above-described sps_sign_data_hiding_enabled_flag.Alternatively, the syntax element of the sign data hiding enabled flagmay be the above-described sh_sign_data_hiding_enabled_flag.

Then, for example, the decoding apparatus may obtain a Transform SkipResidual Coding (TSRC) enabled flag for whether TSRC is enabled for atransform skip block in the current slice. The image information mayinclude a TSRC enabled flag.

For example, the decoding apparatus may obtain the TSRC enabled flagbased on the sign data hiding enabled flag. For example, the TSRCenabled flag may be obtained based on the sign data hiding enabled flagwhose value is 0. That is, for example, when the value of the sign datahiding enabled flag is 0 (i.e., when the sign data hiding enabled flagindicates that sign data hiding is not enabled), the TSRC enabled flagmay be obtained. In other words, for example, when the value of the signdata hiding enabled flag is 0 (i.e., when the sign data hiding enabledflag indicates that sign data hiding is not enabled), the TSRC enabledflag may be signaled. Also, for example, when the value of the sign datahiding enabled flag is 1, the TSRC enabled flag may not be obtained, andthe value of the TSRC enabled flag may be derived as 0. That is, forexample, when the value of the sign data hiding enabled flag is 1, theTSRC enabled flag may not be signaled, and the value of the TSRC enabledflag may be derived as 0.

Here, for example, the TSRC enabled flag may be a flag for whether TSRCis enabled. That is, for example, the TSRC enabled flag may be a flagindicating whether TSRC is enabled for blocks in a slice. In otherwords, for example, the TSRC enabled flag may be a flag indicatingwhether TSRC is enabled for a transform skip block in a slice. Here, theblock may be a coding block (CB) or a transform block (TB). For example,the TSRC enabled flag whose value is 1 may indicate that the TSRC is notenabled, and the TSRC enabled flag whose value is 0 may indicate thatthe TSRC is enabled. Also, for example, the TSRC enabled flag may besignaled in a slice header syntax. The syntax element of the TSRCenabled flag may be the above-describedsh_ts_residual_coding_disabled_flag. The TSRC enabled flag may bereferred to as a TSRC disabled flag.

Meanwhile, for example, the decoding apparatus may obtain a dependentquantization enabled flag. The decoding apparatus may obtain imageinformation including the dependent quantization enabled flag throughthe bitstream. The image information may include the dependentquantization enabled flag. For example, the dependent quantizationenabled flag may be a flag for whether dependent quantization isenabled. For example, the dependent quantization enabled flag mayindicate whether dependent quantization is enabled. That is, forexample, the dependent quantization enabled flag may indicate whetherdependent quantization is enabled for blocks of pictures in a sequence.For example, dependent quantization enabled flag may indicate whether adependent quantization used flag indicating whether dependentquantization is used for the current slice may be present. For example,the dependent quantization enabled flag whose value is 1 may indicatethat the dependent quantization is enabled, and the dependentquantization enabled flag whose value is 0 may indicate that thedependent quantization is not enabled. Also, for example, the dependentquantization enabled flag may be signaled in an SPS syntax, a sliceheader syntax or the like. The syntax element of the dependentquantization enabled flag may be the above-describedsps_dep_quant_enabled_flag.

Also, for example, the decoding apparatus may obtain a transform skipenabled flag. The decoding apparatus may obtain image informationincluding the transform skip enabled flag through the bitstream. Theimage information may include the transform skip enabled flag. Forexample, the transform skip enabled flag may be a flag for whethertransform skip is enabled. For example, the transform skip enabled flagmay indicate whether transform skip is enabled. That is, for example,the transform skip enabled flag may indicate whether transform skip isenabled for blocks of pictures in a sequence. For example, the transformskip enabled flag may indicate whether a transform skip flag may bepresent. For example, the transform skip enabled flag whose value is 1may indicate that the transform skip is enabled, and the transform skipenabled flag whose value is 0 may indicate that the transform skip isnot enabled. That is, for example, the transform skip enabled flag whosevalue is 1 may indicate that the transform skip flag may be present, andthe transform skip enabled flag whose value is 0 may indicate that thetransform skip flag is not present. Also, for example, the transformskip enabled flag may be signaled in a sequence parameter set (SPS)syntax. The syntax element of the transform skip enabled flag may be theabove-described sps_transform_skip_enabled_flag.

Also, for example, the TSRC enabled flag may be obtained based on thesign data hiding enabled flag and/or the transform skip enabled flag.For example, the TSRC enabled flag may be obtained based on the signdata hiding enabled flag whose value is 0, and the transform skipenabled flag whose value is 1. That is, for example, when the value ofthe sign data hiding enabled flag is 0 (that is, the sign data hidingenabled flag indicates that sign data hiding is not enabled), and thevalue of the transform skip enabled flag is 1 (that is, when thetransform skip enabled flag indicates that the transform skip isenabled), the TSRC enabled flag may be obtained (or signaled). Also, forexample, when the value of the transform skip enabled flag is 0, theTSRC enabled flag may not be obtained, and the value of the TSRC enabledflag may be derived as 0. That is, for example, when the value of thetransform skip enabled flag is 0, the TSRC enabled flag may not besignaled, and the value of the TSRC enabled flag may be derived as 0.

Also, for example, the decoding apparatus may obtain residual codinginformation for a current block in the current slice based on the TSRCenabled flag. The decoding apparatus may obtain residual information forthe current block in the current slice based on the TSRC enabled flag.Here, the current block may be a coding block (CB) or a transform block(TB).

For example, the decoding apparatus may determine a residual codingsyntax for the current block in the current slice based on the TSRCenabled flag. For example, the decoding apparatus may determine aresidual coding syntax for the current block as one of the RegularResidual Coding (RRC) syntax and Transform Skip Residual Coding (TSRC)syntax based on the TSRC enabled flag. The RRC syntax may indicate asyntax according to RRC, and the TSRC syntax may indicate a syntaxaccording to TSRC. Also, for example, the current block may be atransform skip block in the current slice. Here, the transform skipblock may mean a block to which transform is not applied.

For example, the residual coding syntax for the current block in thecurrent slice may be determined as the regular residual coding (RRC)syntax based on the TSRC enabled flag whose value is 1. In this case,for example, a transform skip flag for whether the current block istransform-skipped may be obtained based on the transform skip enabledflag whose value is 1, and the value of the transform skip flag maybe 1. For example, the image information may include a transform skipflag for the transform skip block. The transform skip flag may indicatewhether the current block is transform-skipped. That is, the transformskip flag may indicate whether a transform is applied to transformcoefficients of the current block. The syntax element representing thetransform skip flag may be the above-described transform_skip_flag. Forexample, when the value of the transform skip flag is 1, the transformskip flag may indicate that transform is not applied to the currentblock (i.e., transform-skipped), while, when the value of the transformskip flag is 0, the transform skip flag may indicate that transform isapplied to the current block. For example, the value of the transformskip flag for the current block may be 1.

Also, for example, the residual coding syntax for the current block maybe determined as the transform skip residual coding (TSRC) syntax basedon the TSRC enabled flag whose value is 0. Also, for example, thetransform skip flag for whether the current block is transform-skippedmay be obtained, and the residual coding syntax for the current blockmay be determined as the transform skip residual coding (TSRC) syntaxbased on the transform skip flag whose value is 1 and the TSRC enabledflag whose value is 0. Also, for example, the transform skip flag forwhether the current block is transform-skipped may be obtained, and theresidual coding syntax for the current block may be determined as theRegular Residual Coding (RRC) syntax based on the transform skip flagwhose value is 0 and the TSRC enabled flag whose value is 0.

Then, for example, the decoding apparatus may obtain residualinformation of the determined residual coding syntax for the currentblock. For example, residual information of the regular residual coding(RRC) syntax may be obtained based on the TSRC enabled flag whose valueis 1, and residual information of the TSRC syntax may be obtained basedon the TSRC enabled flag whose value is 0. The image information mayinclude residual information.

For example, when the residual coding syntax for the current block isdetermined as the RRC syntax, the decoding apparatus may obtain residualinformation of the RRC syntax for the current block. For example, theresidual information of the RRC syntax may include the syntax elementsshown in Table 2 above.

For example, the residual information of the RRC syntax may includesyntax elements for transform coefficients of the current block. Here,the transform coefficient may be referred to as a residual coefficient.

For example, the syntax elements may include syntax elements such aslast_sig_coeff_x_prefix, last_sig_coeff_y_prefix,last_sig_coeff_x_suffix, last_sig_coeff_y_suffix, sb_coded_flag,sig_coeff_flag, abs_level_gt1_flag, par_level_flag, abs_level_gtX_flag,abs_remainder, dec_abs_level, and/or coeff_sign_flag.

Specifically, for example, the syntax elements may include positioninformation indicating the position of the last non-zero transformcoefficient in the residual coefficient array of the current block. Thatis, the syntax elements may include position information indicating theposition of the last non-zero transform coefficient in a scanning orderof the current block. The position information may include informationindicating a prefix of a column position of the last non-zero transformcoefficient, information indicating a prefix of a row position of thelast non-zero transform coefficient, information indicating a suffix ofa column position of the last non-zero transform coefficient, andinformation indicating a suffix of a row position of the last non-zerotransform coefficient. The syntax elements for the location informationmay be last_sig_coeff_x_prefix, last_sig_coeff_y_prefix,last_sig_coeff_x_suffix, and last_sig_coeff_y_suffix. Meanwhile, thenon-zero transform coefficient may be referred to as a significantcoefficient.

Also, for example, the syntax elements may include a coded subblock flagindicating whether a subblock of the current block includes a non-zerotransform coefficient; a significant coefficient flag indicating whetherthe transform coefficient of the current block is non-zero transformcoefficient; a first coefficient level flag for whether the coefficientlevel for the transform coefficient is greater than a first threshold; aparity level flag for parity of the coefficient level; and/or a secondcoefficient level flag for whether the coefficient level of thetransform coefficient is greater than a second threshold. Here, thecoded sub-block flag may be sb_coded_flag or coded_sub_block_flag; thesignificant coefficient flag may be sig_coeff_flag; the firstcoefficient level flag may be abs_level_gt1_flag or abs_level_gtx_flag;the parity level flag may be par_level_flag; and the second coefficientlevel flag may be abs_level_gt3_flag or abs_level_gtx_flag.

Also, for example, the syntax elements may include information relatedto the coefficient value for value of transform coefficient of thecurrent block. The coefficient value related information may beabs_remainder and/or dec_abs_level.

Also, for example, the syntax elements may include a sign flagindicating a sign of the transform coefficient. The sign flag may becoeff_sign_flag.

Meanwhile, for example, when the sign data hiding is applied to thecurrent block, the sign flag of the first significant transformcoefficient of the current coefficient group (CG) in the current blockmay not be signaled. That is, for example, when the sign data hiding isapplied to the current block, the syntax elements may not include a signflag indicating a sign of the first significant transform coefficient.Meanwhile, for example, whether the sign data hiding is applied to thecurrent block may be derived based on the sign data hiding enabled flag,and/or the position of the first significant transform coefficient andthe position of the last significant transform coefficient of thecurrent CG. For example, when the value of the sign data hiding enabledflag is 1, and the value obtained by subtracting the first significanttransform coefficient position from the last significant transformcoefficient position is greater than 3 (that is, when the value of thesign data hiding enabled flag is 1, and the number of significanttransform coefficients in the current CG is greater than 3), the signdata hiding may be applied to the current CG of the current block.

Additionally, for example, when the residual coding syntax for thecurrent block is determined as the TSRC syntax, the decoding apparatusmay obtain residual information of the TSRC syntax for the currentblock. For example, the residual information of the TSRC syntax mayinclude the syntax elements shown in Table 3 above.

For example, the residual information of the TSRC syntax may includesyntax elements for transform coefficients of the current block. Here,the transform coefficient may be referred to as a residual coefficient.

For example, the syntax elements may include context coded syntaxelements and/or bypass coded syntax elements for a transformcoefficient. The syntax elements may include syntax elements such assig_coeff_flag, coeff_sign_flag, abs_level_gt1_flag, par_level_flag,abs_level_gtX_flag and/or abs_remainder.

For example, the context-coded syntax elements for the transformcoefficient may include a significant coefficient flag indicatingwhether the transform coefficient is a non-zero transform coefficient; asign flag indicating a sign for the transform coefficient; a firstcoefficient level flag for whether the coefficient level for thetransform coefficient is greater than a first threshold; and/or paritylevel flag for parity of the coefficient level for the transformcoefficient. In addition, for example, the context-coded syntax elementsmay include a second coefficient level flag for whether the coefficientlevel of the transform coefficient is greater than a second threshold; athird coefficient level flag for whether the coefficient level of thetransform coefficient is greater than a third threshold; a fourthcoefficient level flag for whether the coefficient level of thetransform coefficient is greater than a fourth threshold; and/or a fifthcoefficient level flag for whether the coefficient level of thetransform coefficient is greater than a fifth threshold. Here, thesignificant coefficient flag may be sig_coeff_flag; the sign flag may becoeff_sign_flag; the first coefficient level flag may beabs_level_gt1_flag; and the parity level flag may be par_level_flag. Inaddition, the second coefficient level flag may be abs_level_gt3_flag orabs_level_gtx_flag; the third coefficient level flag may beabs_level_gt5_flag or abs_level_gtx_flag; the fourth coefficient levelflag may be abs_level_gt7_flag or abs_level_gtx_flag; and the fifthcoefficient level flag may be abs_level_gt9_flag or abs_level_gtx_flag.

Also, for example, the syntax elements bypass-coded for the transformcoefficient may include coefficient level information for the value (orcoefficient level) of the transform coefficient, and/or a sign flagindicating a sign for the transform coefficient. The coefficient levelinformation may be abs_remainder and/or dec_abs_level, and the sign flagmay be coeff_sign_flag.

The decoding apparatus generates a reconstructed picture based on theimage information (S1410). The decoding apparatus may generate areconstructed sample/a reconstructed picture for the current block ofthe current slice based on the image information.

For example, the decoding apparatus may derive a residual sample for thecurrent block based on the residual coding information. For example, thedecoding apparatus may derive transform coefficients of the currentblock based on the residual coding information, and may derive residualsamples of the current block based on the transform coefficients.

For example, the decoding apparatus may derive transform coefficients ofthe current block based on syntax elements of the residual codinginformation. Thereafter, the decoding apparatus may derive residualsamples of the current block based on the transform coefficients. Forexample, when it is derived that transform is not applied to the currentblock based on the transform skip flag, that is, when the value of thetransform skip flag is 1, the decoding apparatus may derive thetransform coefficients as the residual samples of the current block.Alternatively, for example, when being derived without applyingtransform to the current block based on the transform skip flag, thatis, when the value of the transform skip flag is 1, the decodingapparatus may dequantize the transform coefficients to derive theresidual samples of the current block. Alternatively, for example, whenbeing derived while applying transform to the current block in thecurrent slice based on the transform skip flag, that is, when the valueof the transform skip flag for the current block is 0, the decodingapparatus may inverse transform the transform coefficients to derive theresidual samples of the current block. Alternatively, for example, whenbeing derived while applying transform to the current block based on thetransform skip flag, that is, when the value of the transform skip flagis 0, the decoding apparatus may dequantize the transform coefficients,and inverse transform the dequantized transform coefficients to derivethe residual samples of the current block.

Meanwhile, for example, when the sign data hiding is applied to thecurrent block, the sign of the first significant transform coefficientof the current CG in the current block may be derived based on the sumof absolute values of the significant transform coefficients in thecurrent CG. For example, when the sum of the absolute values of thesignificant transform coefficients is even, the sign of the firstsignificant transform coefficient may be derived as a positive value,while, when the sum of absolute values of the significant transformcoefficients is odd, the sign of the first significant transformcoefficient may be derived as a negative value.

Then, for example, the decoding apparatus may generate a reconstructedpicture based on the residual sample. Meanwhile, for example, thedecoding apparatus may prediction information for the current block, andmay derive a prediction sample of the current block based on theprediction information. For example, the decoding apparatus may derive aprediction sample of the current block based on an inter prediction modeor an intra prediction mode determined based on the predictioninformation. Then, for example, the decoding apparatus may generate areconstructed sample and/or a reconstructed picture of the current blockbased on the prediction sample and the residual sample. For example, thedecoding apparatus may generate the reconstructed sample throughaddition of the prediction sample and the residual sample.

After this, as described above, an in-loop filtering procedure such asan ALF procedure, SAO and/or deblocking filtering may be applied asneeded to the reconstructed picture in order to improvesubjective/objective video quality.

FIG. 15 briefly illustrates a decoding apparatus for performing an imagedecoding method according to the present disclosure. The methoddisclosed in FIG. 14 may be performed by the decoding apparatusdisclosed in FIG. 15 . Specifically, for example, the entropy decoder ofthe decoding apparatus of FIG. 15 may perform S1400 of FIG. 14 ; and theresidual processor of the decoding apparatus of FIG. 15 may performS1410 of FIG. 14 . Additionally, although not shown, the process ofreceiving prediction information for the current block may be performedby an entropy decoder of the decoding apparatus of FIG. 15 , and theprocess of deriving the prediction sample of the current block based onthe prediction information may be performed by the predictor of thedecoding apparatus of FIG. 15 .

According to this document, as described above, it is possible toimprove efficiency of residual coding.

Additionally, according to this document, the TSRC enabled flag can besignaled depending on the sign data hiding enabled flag, and throughthis, the coding efficiency can be improved by preventing sign datahiding from being used for the transform skip block for which TSRC isnot enabled, and the overall residual coding efficiency can be improvedby reducing the bit amount to be coded.

Additionally, according to this document, the TSRC enabled flag can besignaled depending on the transform skip enabled flag and the sign datahiding enabled flag, and through this, the coding efficiency can beimproved by preventing sign data hiding from being used for thetransform skip block for which TSRC is not enabled, and the overallresidual coding efficiency can be improved by reducing the bit amount tobe coded.

In the above-described embodiment, the methods are described based onthe flowchart having a series of steps or blocks. The present disclosureis not limited to the order of the above steps or blocks. Some steps orblocks may occur simultaneously or in a different order from other stepsor blocks as described above. Further, those skilled in the art willunderstand that the steps shown in the above flowchart are notexclusive, that further steps may be included, or that one or more stepsin the flowchart may be deleted without affecting the scope of thepresent disclosure.

The embodiments described in this specification may be performed bybeing implemented on a processor, a microprocessor, a controller or achip. For example, the functional units shown in each drawing may beperformed by being implemented on a computer, a processor, amicroprocessor, a controller or a chip. In this case, information forimplementation (e.g., information on instructions) or algorithm may bestored in a digital storage medium.

In addition, the decoding apparatus and the encoding apparatus to whichthe present disclosure is applied may be included in a multimediabroadcasting transmission/reception apparatus, a mobile communicationterminal, a home cinema video apparatus, a digital cinema videoapparatus, a surveillance camera, a video chatting apparatus, areal-time communication apparatus such as video communication, a mobilestreaming apparatus, a storage medium, a camcorder, a VoD serviceproviding apparatus, an Over the top (OTT) video apparatus, an Internetstreaming service providing apparatus, a three-dimensional (3D) videoapparatus, a teleconference video apparatus, a transportation userequipment (e.g., vehicle user equipment, an airplane user equipment, aship user equipment, etc.) and a medical video apparatus and may be usedto process video signals and data signals. For example, the Over the top(OTT) video apparatus may include a game console, a blue-ray player, aninternet access TV, a home theater system, a smart phone, a tablet PC, aDigital Video Recorder (DVR), and the like.

Furthermore, the processing method to which the present disclosure isapplied may be produced in the form of a program that is to be executedby a computer and may be stored in a computer-readable recording medium.Multimedia data having a data structure according to the presentdisclosure may also be stored in computer-readable recording media. Thecomputer-readable recording media include all types of storage devicesin which data readable by a computer system is stored. Thecomputer-readable recording media may include a BD, a Universal SerialBus (USB), ROM, PROM, EPROM, EEPROM, RAM, CD-ROM, a magnetic tape, afloppy disk, and an optical data storage device, for example.Furthermore, the computer-readable recording media includes mediaimplemented in the form of carrier waves (e.g., transmission through theInternet). In addition, a bit stream generated by the encoding methodmay be stored in a computer-readable recording medium or may betransmitted over wired/wireless communication networks.

In addition, the embodiments of the present disclosure may beimplemented with a computer program product according to program codes,and the program codes may be performed in a computer by the embodimentsof the present disclosure. The program codes may be stored on a carrierwhich is readable by a computer.

FIG. 16 illustrates a structural diagram of a contents streaming systemto which the present disclosure is applied.

The content streaming system to which the embodiment(s) of the presentdisclosure is applied may largely include an encoding server, astreaming server, a web server, a media storage, a user device, and amultimedia input device.

The encoding server compresses content input from multimedia inputdevices such as a smartphone, a camera, a camcorder, etc. Into digitaldata to generate a bitstream and transmit the bitstream to the streamingserver. As another example, when the multimedia input devices such assmartphones, cameras, camcorders, etc. directly generate a bitstream,the encoding server may be omitted.

The bitstream may be generated by an encoding method or a bitstreamgenerating method to which the embodiment(s) of the present disclosureis applied, and the streaming server may temporarily store the bitstreamin the process of transmitting or receiving the bitstream.

The streaming server transmits the multimedia data to the user devicebased on a user's request through the web server, and the web serverserves as a medium for informing the user of a service. When the userrequests a desired service from the web server, the web server deliversit to a streaming server, and the streaming server transmits multimediadata to the user. In this case, the content streaming system may includea separate control server. In this case, the control server serves tocontrol a command/response between devices in the content streamingsystem.

The streaming server may receive content from a media storage and/or anencoding server. For example, when the content is received from theencoding server, the content may be received in real time. In this case,in order to provide a smooth streaming service, the streaming server maystore the bitstream for a predetermined time.

Examples of the user device may include a mobile phone, a smartphone, alaptop computer, a digital broadcasting terminal, a personal digitalassistant (PDA), a portable multimedia player (PMP), navigation, a slatePC, tablet PCs, ultrabooks, wearable devices (ex. Smartwatches, smartglasses, head mounted displays), digital TVs, desktops computer, digitalsignage, and the like. Each server in the content streaming system maybe operated as a distributed server, in which case data received fromeach server may be distributed.

The claims described in the present disclosure may be combined invarious ways. For example, the technical features of the method claimsof the present disclosure may be combined to be implemented as anapparatus, and the technical features of the apparatus claims of thepresent disclosure may be combined to be implemented as a method. Inaddition, the technical features of the method claim of the presentdisclosure and the technical features of the apparatus claim may becombined to be implemented as an apparatus, and the technical featuresof the method claim of the present disclosure and the technical featuresof the apparatus claim may be combined to be implemented as a method.

What is claimed is:
 1. An image decoding method performed by a decodingapparatus, the method comprising: obtaining image information; andgenerating a reconstructed picture based on the image information,wherein the obtaining the image information comprises: obtaining a signdata hiding enabled flag for whether sign data hiding is enabled for acurrent slice; obtaining a Transform Skip Residual Coding (TSRC) enabledflag for whether TSRC is enabled for a transform skip block in thecurrent slice, wherein the TSRC enabled flag is obtained based on thesign data hiding enabled flag.
 2. The method of claim 1, wherein theTSRC enabled flag is obtained based on the sign data hiding enabled flagwhose value is
 0. 3. The method of claim 2, wherein when the value ofthe sign data hiding enabled flag is 1, the TSRC enabled flag is notobtained, and a value of the TSRC enabled flag is derived as
 0. 4. Themethod of claim 1, wherein the sign data hiding enabled flag whose valueis 1 represents that the sign data hiding is enabled, and wherein thesign data hiding enabled flag whose value is 0 represents that the signdata hiding is not enabled.
 5. The method of claim 4, wherein when thesign data hiding is enabled, a sign of a first significant transformcoefficient of a current coefficient group (CG) in the transform skipblock is derived based on the sum of absolute values of significanttransform coefficients in the current CG.
 6. The method of claim 5,wherein when the sign data hiding is enabled, a sign flag for the firstsignificant transform coefficient is not obtained.
 7. The method ofclaim 1, wherein the TSRC enabled flag is obtained in a slice headersyntax.
 8. The method of claim 1, wherein the obtaining the imageinformation further comprises obtaining a transform skip enabled flagfor whether transform skip is enabled, wherein the TSRC enabled flag isobtained based on the sign data hiding enabled flag and the transformskip enabled flag.
 9. The method of claim 8, wherein the TSRC enabledflag is obtained based on the sign data hiding enabled flag whose valueis 0 and the transform skip enabled flag whose value is
 1. 10. Themethod of claim 9, wherein when the value of the transform skip enabledflag is 0, the TSRC enabled flag is not obtained, and a value of theTSRC enabled flag is derived as
 0. 11. An image encoding methodperformed by an encoding apparatus, the method comprising: generating areconstructed picture for a current slice; and encoding imageinformation for the current slice, wherein the encoding imageinformation comprises: encoding a sign data hiding enabled flag forwhether sign data hiding is enabled for the current slice; and encodinga Transform Skip Residual Coding (TSRC) enabled flag for whether TSRC isenabled for a transform skip block in the current slice based on thesign data hiding enabled flag.
 12. The method of claim 11, wherein theTSRC enabled flag is encoded based on the sign data hiding enabled flagwhose value is
 0. 13. The method of claim 11, wherein the encoding theimage information further comprises encoding a transform skip enabledflag for whether transform skip is enabled, wherein the TSRC enabledflag is encoded based on the sign data hiding enabled flag and thetransform skip enabled flag.
 14. The method of claim 13, wherein theTSRC enabled flag is encoded based on the sign data hiding enabled flagwhose value is 0 and the transform skip enabled flag whose value is 1.15. A non-transitory computer-readable storage medium storing abitstream including image information causing a decoding apparatus toperform the following steps: obtaining image information; and generatinga reconstructed picture based on the image information, wherein theobtaining the image information includes: obtaining a sign data hidingenable flag for whether sign data hiding is enable for a current slice;and obtaining a Transform Skip Residual Coding (TSRC) enable flag forwhether TSRC is enable for a transform skip block in the current slice,wherein the TSRC enable flag is obtained based on the sign data hidingenable flag.